# Does good 'flow and distribution' always require high current?



## Wookii (27 Apr 2020)

Good 'flow and distribution' is a mantra I see throughout this forum, along with the regular suggestion of filter (or circulation pump) capacity of 10x tank volume, particularly with respect to high tech tanks to achieve sufficient circulation of injected CO2 and fertilisers to all areas of the tank.

Whilst this makes perfect practical sense to me, I can't help but notice that this often results in a fair amount of 'current' throughout most of the tank - in my own aquarium, in a circular pattern around the tank, obviously most strongly in the face of the tank adjacent to the filter outlet.

I also observe in my own set-up, that when I switch off the filter and the current stops, there appears to be much more natural and exploratory behaviour from the shrimp and fish (and I think not just because they associate the lack of current with feeding times). The still water version of the aquarium makes for a much more interesting viewing experience than the running water version.

With this in mind, my question is, is it possible to design a system that achieves good flow and distribution of CO2 and ferts, without the high current?


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## kilnakorr (27 Apr 2020)

Following this one.

I personally struggle with this myself.
The high flow to deliver nutrients to the plants makes sense, but I hate the looks. Especially in larger/longer tanks, where you need really high flow to get the flow  to the other end (or several smaller powerheads).

I'm so open for ideas (but not spraybars as they require massive filters)


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## Sammy Islam (27 Apr 2020)

I think not many of us actually achieve a 10x turnover, most probably only like 5x, but makes sense to aim for 10x as by the time the filter has media inside and gunk its probably half that.

For my tank that's full of rotala at the back i have to be careful not the stunt it from battering it with harsh flow. So for me flow pattern/circulation is probably more important. As long as i have decent flow and co2 and ferts are reaching all my plants then i should be good regardless of how quick it is going around?

Also a similar thing with increasing co2 and flow. The whole drop checker v "1 point drop", by the time we reach a "1point drop" the drop checker is most likely yellow when we are suppose to be at green. Then when problems start like co2 related algae we up the co2 even more and stress the fish and it seems like a never ending battle even though we have "more" co2 than we are "supposed" to.


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## kilnakorr (27 Apr 2020)

Sammy Islam said:


> As long as i have decent flow and co2 and ferts are reaching all my plants then i should be good regardless of how quick it is going around?


That is exactly what is needed.
However, I have yet to find a solution were I can get a nice gentle flow all over.
I cannot seem to get a gentle sway in one end without a storm at the other end.
Main problem in my case, is that flow needs to be started at the opposite end of the tank to avoid blasting stemplants around.

I guess both @Wookii and myself are looking for solutions to generate gentle flow.


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## Zeus. (27 Apr 2020)

Wookii said:


> With this in mind, my question is, is it possible to design a system that achieves good flow and distribution of CO2 and ferts, without the high current?



Yes, its having a variable flow/current in the tank. So flow is optimal to suit the plants needs at different times of day, the first 4-5 hours of the photoperiod are the most critical as thats when plants uptake the most CO2 so good flow and stable [CO2] is the key, but after plants slow down their uptake the flow/current can also be reduced as well IMO. I achieve this with Twin Maxspect Gyres which have a controller with 24 slots in a schedule so flow can be varied between 0-100% in 5% increments so towards end of photoperiod flow on restively low and at night on gentle flow, as soon as CO2 comes on flow ramps up ready for lights coming on. Having twin Gyres helps too as at night one can be off of a couple of hours at a time and cleanup crew do their work. During the day havings them alternate output moves the dead spots around also.


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## Ghettofarmulous (27 Apr 2020)

I am in the midst of experimenting. I mashed together a spray bar and I’m happy with the mist of Co2 reaching all areas of my flex 57 but I don’t ever we see any of my Neo or Amano shrimp in the front of the tank. I would think a desirable effect is complete Co2 dissolved in the water column then high flow to drive Co2 bubbles down is not required. Nutrients I believe are much easier to distribute as eventually the mix is homogenised.


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## Wookii (27 Apr 2020)

To be honest part of me asking the question - along with the observation of the behaviour of the occupants of my current tank - is that I have recently acquired a new 1500 x 450 x 450 tank, and want to plan such a low current design.

So running some ideas off the top of my head.

If we take my new tank as an example, thats 300 litres. A common configuration would be to have an inlet and outlet in two opposite corners. So assuming 10x turnover, that’s 1500 litre per hour out of each outlet.

That going to create a high level of current out those outlets, but probably achieves decent distribution via a circular flow.

If we increase the number to outlets to, say, three in each opposite corner at different heights (let’s ignore the practicalities for now - this is a theoretical exercise for the moment), we reduce the output of each to 500 litres per hour. That should see the current significantly reduced.

The problem is, the current my be insufficient to maintain the circular flow, and dead spots could be created.

So how about we put all six outlets at one end, each on a slightly different azimuth and elevation (to give even spread across the tank width and height) and have all the inlets at the opposite end. If we are maintaining our 10x turnover, then we should have less dead spots, as 3000 litres of water is entering the tank at one end, and leaving it at the other, every hour - like a wall of water travelling completely down the tank. Our only possible issue now, is hardscape causing dead spots along that line of travel, no? (I’m quite sure there are things I haven’t even thought of here, I’ve just thinking [writing] aloud). 

I’ve even considered whether it would be possible to have pipe work under the substrate feeding sprinkler type head at various points (hidden from view by hardscape of course) allowing slow outflow across the bottom of the tank - but the more I think about that, the more it feels like a maintenance nightmare.

Anyone have any other ideas?


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## Wookii (27 Apr 2020)

Sammy Islam said:


> I think not many of us actually achieve a 10x turnover, most probably only like 5x, but makes sense to aim for 10x as by the time the filter has media inside and gunk its probably half that.



I agree - I suspect the 10x rules has been lost a little in translation, and is more guidance for selecting a pump/filter canister rated for 10x the tank volume, though in reality it will never deliver that.

In my own tank I’m running a filter allegedly rated at 20x my tank volume (though I don’t believe it is anywhere near that in real use) plus an in tank skimmer - so I am over egging the pudding a bit anyway.



Sammy Islam said:


> For my tank that's full of rotala at the back i have to be careful not the stunt it from battering it with harsh flow. So for me flow pattern/circulation is probably more important. As long as i have decent flow and co2 and ferts are reaching all my plants then i should be good regardless of how quick it is going around?



That’s kind of the point though we want flow to ensure the good stuff reaches that plants, but we (I) want to achieve that with the minimum of ‘current’ (by that I mean the maximum speed/pressure of water at any one point).



Sammy Islam said:


> Also a similar thing with increasing co2 and flow. The whole drop checker v "1 point drop", by the time we reach a "1point drop" the drop checker is most likely yellow when we are suppose to be at green. Then when problems start like co2 related algae we up the co2 even more and stress the fish and it seems like a never ending battle even though we have "more" co2 than we are "supposed" to.



To be fair the CO2 side is a different topic - I found having a good quality Ph monitor/probe has been a god send in sorting that out and eliminating the 2 hour drop checker delay - but thats for another thread.


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## Wookii (27 Apr 2020)

Zeus. said:


> Yes, its having a variable flow/current in the tank. So flow is optimal to suit the plants needs at different times of day, the first 4-5 hours of the photoperiod are the most critical as thats when plants uptake the most CO2 so good flow and stable [CO2] is the key, but after plants slow down their uptake the flow/current can also be reduced as well IMO. I achieve this with Twin Maxspect Gyres which have a controller with 24 slots in a schedule so flow can be varied between 0-100% in 5% increments so towards end of photoperiod flow on restively low and at night on gentle flow, as soon as CO2 comes on flow ramps up ready for lights coming on. Having twin Gyres helps too as at night one can be off of a couple of hours at a time and cleanup crew do their work. During the day havings them alternate output moves the dead spots around also.



Variable flow is a good idea to have period of lower current - but in the first instance I want to see if there is a solution for having constant low current.

Out of interest do you notice different behaviour of your fish and shrimp when the current is reduced?


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## Zeus. (27 Apr 2020)

Wookii said:


> Out of interest do you notice different behaviour of your fish and shrimp when the current is reduced?



Yes


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## foxfish (27 Apr 2020)

I set up a low water movement tank a few years back, it was based around an under gravel filter with reverse flow.
I just used an external C02 reactor  and fed the C02 enriched water up through the gravel.
It was still quite a high flow rate but due the upward diffused flow there was very little visible movement.
In fact I made a short video that is on this forum somewhere.


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## kilnakorr (28 Apr 2020)

I rewatched this video on filtration last night.


In short, they say to stuck filter with lots of bio media, and for bigger tanks and a turnover of 2-3 times is enough.


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## foxfish (28 Apr 2020)

You only have to think about it in a logical way, if you are injecting  C02 and you want that C02 to reach all the plants in the tank, then you need to distribute the enriched water amongst all the plants.
If you only have one plant then you would only need to direct the flow to that plant but if you have a big tank full dense foliage that you need a very good and evenly distributed flow.


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## Zeus. (28 Apr 2020)

kilnakorr said:


> I rewatched this video on filtration last night.
> 
> 
> In short, they say to stuck filter with lots of bio media, and for bigger tanks and a turnover of 2-3 times is enough.




They have such amazing tanks, there are even better if you visit the showroom so the vid does suck you in, then they land the sales pitch

However I completely disagree about the bio media bio media for fluval 305. Medium course sponges all the way. They do forget to mention the largest bio filtration in their tanks- the plants roots

Notice they choice of ferts -ADA most expensive ferts per ppm of nutrients on the planet!!





As for the flow well having seen there tanks I was amazed at the low flow and it works for them, maybe its to do with the re mineralised RO water, or the excellant maintenance regime.

Dont be drawn by the sales pitch, follow the science


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## jaypeecee (28 Apr 2020)

Hi Folks,

Interesting thread.

I have a bit of a problem with terminology here. Specifically, _flow_ and _current_. For me, they are one and the same. But, I suspect that the word 'current' is being used here to denote _rate of flow_, i.e. the _velocity/speed_ at which the water is moving. I think of flow or current as electrons in a wire or water in a pipe. High flow can be achieved by 'pushing harder', be that the battery voltage or water pressure. It seems to me that, perhaps, what is needed in an aquarium is a large volume of water moving relatively slowly. Not a small volume of water running a 'four-minute mile'. I'm looking at this with a view to obtaining optimum CO2 and ferts distribution. Am I on the right track?

JPC


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## Wookii (28 Apr 2020)

foxfish said:


> You only have to think about it in a logical way, if you are injecting  C02 and you want that C02 to reach all the plants in the tank, then you need to distribute the enriched water amongst all the plants.
> If you only have one plant then you would only need to direct the flow to that plant but if you have a big tank full dense foliage that you need a very good and evenly distributed flow.



Agree completely - the need to distribute the CO2 isn’t under question. The question is, is there a way to do this where the current/speed/velocity of the water is slow, rather than the typical single point source high velocity filter outlet. Your under gravel system was a perfect example, but there must be others.


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## Wookii (28 Apr 2020)

kilnakorr said:


> I rewatched this video on filtration last night.
> 
> 
> In short, they say to stuck filter with lots of bio media, and for bigger tanks and a turnover of 2-3 times is enough.







Zeus. said:


> They have such amazing tanks, there are even better if you visit the showroom so the vid does suck you in, then they land the sales pitch
> 
> However I completely disagree about the bio media bio media for fluval 305. Medium course sponges all the way. They do forget to mention the largest bio filtration in their tanks- the plants roots
> 
> ...




I think the Green Aqua videos are great, really well put together and professionally produced, and Balazs is clearly a charismatic presenter - but I agree, you do have to see ‘through’ some of the marketing - which is fair enough I guess, they’re not doing them for charity!

I don’t want to get too hung up on the turnover thing - as @foxfish says, it’s a simple requirement to get CO2 and nutrient rich water to all plants in the aquarium. As @Zeus. says, the plants are the main biological filters, so as long as waste is being sufficiently processed, and full distribution of CO2 etc is being achieved, actual turnover shouldn’t matter,

The question again to reiterate, is can we achieve that manner with low current/velocity?


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## foxfish (28 Apr 2020)

I did another one with a matrix of pipes on a bare bottom tank and potted plants, unfortunately the videos were on photobucket and I can’t find the originals as they were stored on an old laptop long buried .

Anyway the standard way of using a full length  spray bar is designed to move the water column as a whole mass.
The concept is to push the water along the surface and down the front glass along the bottom and back up the rear.
If you can get that rolling effect then I think you will have good success.


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## Wookii (28 Apr 2020)

jaypeecee said:


> Hi Folks,
> 
> Interesting thread.
> 
> I have a bit of a problem with terminology here. Specifically, _flow_ and _current_. For me, they are one and the same. But, I suspect that the word 'current' is being used here to denote _rate of flow_, i.e. the _velocity/speed_ at which the water is moving. I think of flow or current as electrons in a wire or water in a pipe. High flow can be achieved by 'pushing harder', be that the battery voltage or water pressure.



I don’t think if ‘flow’ and ‘current’ as being the same thing - a large river can have high flow, and low current, and a small stream can have low flow and high current. I think of flow as volume, and current as speed/velocity/turbulence.

Thats said, I don’t want to split hairs too much on definitions, though I do agree, I didn’t like using the term ‘current’ - I just couldn’t think of anything else. Velocity, now you’ve used it your post, is much more appropriate.



jaypeecee said:


> It seems to me that, perhaps, what is needed in an aquarium is a large volume of water moving relatively slowly. Not a small volume of water running a 'four-minute mile'. I'm looking at this with a view to obtaining optimum CO2 and ferts distribution. Am I on the right track?
> 
> JPC



Yes, I think you are on the right track - varying the volume could help achieve greater distribution, if our aim is to reduce the velocity. However I think we also need to consider the outlet design - starting with a blank piece of paper - in how we achieve sufficient distribution with low outlet velocity.


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## foxfish (28 Apr 2020)

I found this old thread where I used a return under a perforated plate but I did use a big power head flow extra flow as well, I think I wanted the effect of moving plants but anyway it might give you some inspiration .
(No videos working though) https://www.ukaps.org/forum/threads/disaster-or-a-new-dawn.15812/


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## Zeus. (28 Apr 2020)

jaypeecee said:


> I have a bit of a problem with terminology here. Specifically, _flow_ and _current_.



Yes it can be tricky just like Volts ,Amps and Watts. I think if it as Flow is the Volts eg speed/direction of the water, Current is the Amps eg amount/magnitude of water, the Watts is the Vector/turnover which has the  magnitude and direction the amount of water moving



Wookii said:


> actual turnover shouldn’t matter



IMO its critical as its the turnover that delivers the CO2, Carbon is the main element/nutrient in a plants structure, so it needs Carbon the most esp in high light, so we need to deliver the Carbon to the plants ideally at a steady concentration.


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## Wookii (28 Apr 2020)

Zeus. said:


> IMO its critical as its the turnover that delivers the CO2, Carbon is the main element/nutrient in a plants structure, so it needs Carbon the most esp in high light, so we need to deliver the Carbon to the plants ideally at a steady concentration.



Exactly, it’s not the turnover that’s critical then is it, it’s the delivery of the CO2 and nutrients.

If you are achieving good distribution of the carbon with, for example, 5x turnover, then 10x turnover is unnecessary. If you aren’t achieving good distribution with a 5x turnover (resultant poor localised plant growth or localised algae) then a higher multiplier, or a change in the distribution design, might be more appropriate.

A specific turnover multiplier is not an appropriate target in and of itself, that was my point, more it’s a means to and end.


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## Zeus. (28 Apr 2020)

Wookii said:


> it’s not the turnover that’s critical then is it, it’s the delivery of the CO2 and nutrients.



Yes/No - depends on how we think of it, but as long as CO2 is non limiting we are fine as plants have enough CO2



Wookii said:


> specific turnover multiplier is not an appropriate target



Correct as its a guide as we cant be specific about the turnover  as for some x5 is fine and others its not, hence the general advice is x10 as too much is better than not enough esp in CO2 injected tanks


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## kilnakorr (28 Apr 2020)

Zeus. said:


> Medium course sponges all the way. They do forget to mention the largest bio filtration in their tanks- the plants roots


Could be true, and I believe most people will agree.
However, I have run into a little algea in my new setup even though I run with lower lights and much more flow/current then prior.
Only difference is alot less bio media in the filter.

I just filled up the filter with bio media (roughly 5 liters worth of eheim substratpro), and reduced flow in the tank by 75%, just to see what happens.
Will take sometime to see if anything happens with the algea.


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## jaypeecee (28 Apr 2020)

Zeus. said:


> Yes it can be tricky just like Volts ,Amps and Watts. I think if it as Flow is the Volts eg speed/direction of the water, Current is the Amps eg amount/magnitude of water, the Watts is the Vector/turnover which has the magnitude and direction the amount of water moving



Hi @Zeus

In electrical/electronic terminology, electromotive force (measured in Volts) is the driving force that pushes electrons around a circuit. The electrons carry a charge, measured in Coulombs. The rate at which charge flows is what we call 'current' (measured in Amps). Watts is the unit of power and equates to Volts x Amps. Now, fluid dynamics is not my forte but Volts is akin to the height of a water fall. The rate at which the volume of water is falling is akin to electrical current.

My apologies to the OP for my digression.

JPC


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## jaypeecee (28 Apr 2020)

Hi Folks,

Wouldn't it be nice if we didn't have to rely on additional propeller pumps, powerheads, etc. in our tanks? If only an external filter could accomplish this task on its own. Whilst it's one thing to deliver the water through a spray bar, the rate at which water returns to the external filter is often limited by just one small inlet. Or, perhaps, other aquarists do things differently.

JPC


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## Wookii (28 Apr 2020)

jaypeecee said:


> Hi Folks,
> 
> Wouldn't it be nice if we didn't have to rely on additional propeller pumps, powerheads, etc. in our tanks? If only an external filter could accomplish this task on its own. Whilst it's one thing to deliver the water through a spray bar, the rate at which water returns to the external filter is often limited by just one small inlet. Or, perhaps, other aquarists do things differently?
> 
> JPC



I personally plan to use a sump on this next tank, so I can fit pretty much any size pump necessary. That’s why I want to start with a blank sheet of paper in terms of outlet and flow/distribution design.


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## jaypeecee (28 Apr 2020)

Wookii said:


> I personally plan to use a sump on this next tank, so I can fit pretty much any size pump necessary. That’s why I want to start with a blank sheet of paper in terms of outlet and flow/distribution design.



Hi @Wookii 

I've never had to consider a sump arrangement for any of my tanks because their size simply doesn't warrant it. If you go down this route, does that mean drilling holes in the bottom of the tank?

JPC


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## Wookii (28 Apr 2020)

jaypeecee said:


> Hi @Wookii
> 
> I've never had to consider a sump arrangement for any of my tanks because their size simply doesn't warrant it. If you go down this route, does that mean drilling holes in the bottom of the tank?
> 
> JPC



Tank size doesn’t matter that much, see here:

https://www.ukaps.org/forum/threads/taking-a-sump-back-in-five-minutes.59010/

The holes will be near the top edge of one face to allow fitting of a weir and overflow box. Take a look at this thread as @DeepMetropolis has just moved to a sump on an already installed tank:

https://www.ukaps.org/forum/threads/to-sump-or-n̶o̶t̶-to-sump-journal.60005/


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## jaypeecee (28 Apr 2020)

Hi @Wookii 

Looks good but my DIY skills are now not up to the job.

JPC


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## Wookii (1 May 2020)

So anyway, my research into a low velocity, good distribution design continues. I stumbled across this Green Aqua video, where they show their sump filtered tank. The flow seems woefully insufficient, and  is barely noticeable (see from 5 minutes in), unless they turned the pump down for the video?



Likewise here in the video of Tom Barr's tanks - if you look at the video from 8:30 onwards (if you can cope with the jarring camera wobble and over-exposure) - there is precious little water movement in the tank. There is surface ripple, but the stems and leaves don't appear to move much at all:



Maybe my perception of what is representative of high levels of flow and good distribution are incorrect? My expectation would be that plants in both tanks would need to see a lot more movement. If anyone else has any videos which demonstrate adequate flow velocity for a success planted tank, I'd welcome seeing them so I can maybe reset my expectations.


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## jaypeecee (1 May 2020)

Wookii said:


> So anyway, my research into a low velocity, good distribution design continues.



Hi @Wookii 

I discovered a scientific paper that investigates the effect of water current velocity on a particular species of aquatic plant. The link below will take you to the Abstract of the relevant paper:

https://www.sciencedirect.com/science/article/abs/pii/0304377083900281

It would appear that 1 cm/sec was optimum for this plant.

Hope this is helpful.

JPC


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## Wookii (1 May 2020)

jaypeecee said:


> Hi @Wookii
> 
> I discovered a scientific paper that investigates the effect of water current velocity on a particular species of aquatic plant. The link below will take you to the Abstract of the relevant paper:
> 
> ...



Thanks JCP - I'll have to try and read through that later. The abstract was interesting though:



> Apparent photosynthesis was stimulated by increasing velocities and a maximum rate was reached at 8–12 mm s−1. Increasing the velocity to 20 and 40 mm s−1 reduced the photosynthetic rates by 5–30% and 13–29%, respectively. It is suggested that the inhibition of photosynthesis at high velocities is caused by agitation of the incubated plant material.



Whilst I have no idea how those flow velocities relates to real world aquarium flow (i.e. what those levels of flow would look like in practice), it would seem to suggest that too much flow velocity could be counter productive. I guess it would be possible to put a ruler in the water and see just how fast a small object travels, say, 100mm to calculate a approximate flow rate.


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## jaypeecee (1 May 2020)

Wookii said:


> Whilst I have no idea how those flow velocities relates to real world aquarium flow (i.e. what those levels of flow would look like in practice), it would seem to suggest that too much flow velocity could be counter productive. I guess it would be possible to put a ruler in the water and see just how fast a small object travels, say, 100mm to calculate a approximate flow rate.



Hi @Wookii 

Yes, there appears to be a 'sweet spot' - neither too slow nor too fast. Following on from your suggestion, the 'small object' could be a CO2 bubble. And if the movement of this CO2 bubble was captured on video, the water current velocity could be estimated/measured.

JPC


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## Zeus. (1 May 2020)

Wookii said:


> So anyway, my research into a low velocity, good distribution design continues. I stumbled across this Green Aqua video, where they show their sump filtered tank. The flow seems woefully insufficient, and  is barely noticeable (see from 5 minutes in), unless they turned the pump down for the video?
> 
> 
> 
> ...




Yes been to Green Aqua and seen the flow, @alto often posts about the low flow rates in his tanks without any issues, in both these we have very experienced folk looking after their tanks, however the general consensus is still x10. Until we see folk not having issues in tanks which can be flow related I can't see the general advise changing to the new people entering the hobby.


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## Wookii (1 May 2020)

Zeus. said:


> Yes been to Green Aqua and seen the flow, @alto often posts about the low flow rates in his tanks without any issues, in both these we have very experienced folk looking after their tanks, however the general consensus is still x10. Until we see folk not having issues in tanks which can be flow related I can't see the general advise changing to the new people entering the hobby.



Agreed - though we are conflating flow/velocity and turnover again - for simplicity if we assume for the remainder of the thread that turnover is maintained at 10x so we can remove it from the discussion, then the discussion is about only velocity e.g. 10x turnover out of one small outlet, versus 10x turnover out of multiple or large outlets such that velocity is reduced, but distribution is maintained. That's the goal I'm trying to establish a design to achieve.

As an aside though, it would be interesting to understand why those tanks from those experienced aquarists achieve good algae free plant growth with minimal apparent velocity.


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## kilnakorr (1 May 2020)

I believe the 10x turnover is like a lot of other things in this hobby: guidelines to avoid common mistakes.
With a 10x turnover chances of dead spots are very limited. If you are experienced you can get away with much less.
Just as light. Give a novice 200 par at substrate level and chances of algae is pretty high, but experienced people can get away with it.


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## jaypeecee (1 May 2020)

Wookii said:


> If you are achieving good distribution of the carbon with, for example, 5x turnover, then 10x turnover is unnecessary. If you aren’t achieving good distribution with a 5x turnover (resultant poor localised plant growth or localised algae) then a higher multiplier, or a change in the distribution design, might be more appropriate.



Hi @Wookii 

I am 100% with you on this. It is perfectly conceivable to have a filtration inlet and outlet combination where 'pockets' of water are stationary. A spray bar will help with distribution of water on the way into the tank. But, you'll have to help me here - is an immersed multiple-inlet pipe then used to feed the aquarium water back to the filter? Or, do most people use a single inlet (as I do on my 125 litre tank)? If we had access to suitable-sized tanks and inlet/outlet combinations, all that would be necessary would be to put one drop of dye in the water and watch how it disperses.

JPC


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## sparkyweasel (1 May 2020)

jaypeecee said:


> It would appear that 1 cm/sec was optimum for this plant.


The plant being _Callitriche stagnalis _which naturally grows in still or slow-moving waters. 
Here's a paper that looks at different species of stream plants, I can't access the full text at the moment, but it might be interesting to anyone who can.
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2006.01573.x.


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## jaypeecee (1 May 2020)

Hi Folks,

I think a lot can be gleaned by closely observing the region in the immediate vicinity of the filter inlet(s) in the tank. How close to the filter inlet(s) do particles need to be to get sucked in? On my 125 litre tank using an Eheim Ecco Pro 130, this has caused me some concern.

JPC


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## Wookii (1 May 2020)

jaypeecee said:


> Hi @Wookii
> 
> I am 100% with you on this. It is perfectly conceivable to have a filtration inlet and outlet combination where 'pockets' of water are stationary. A spray bar will help with distribution of water on the way into the tank. But, you'll have to help me here - is an immersed multiple-inlet pipe then used to feed the aquarium water back to the filter? Or, do most people use a single inlet (as I do on my 125 litre tank)? If we had access to suitable-sized tanks and inlet/outlet combinations, all that would be necessary would be to put one drop of dye in the water and watch how it disperses.
> 
> JPC



I guess most people use a single inlet and single outlet per canister filter. On a larger tank they may have two canister filters and have two inlets and two outlet.

However for the purposes for designing a low velocity system, let’s just dispense with any restrictions like that. Let’s just assume we can choose any number, size, style and position of inlets and outlets as is necessary to achieve the design goal.

I appreciate any design would be dependent on hardscape also, but let start simply.


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## Wookii (1 May 2020)

jaypeecee said:


> Hi Folks,
> 
> I think a lot can be gleaned by closely observing the region in the immediate vicinity of the filter inlet(s) in the tank. How close to the filter inlet(s) do particles need to be to get sucked in? On my 125 litre tank using an Eheim Ecco Pro 130, this has caused me some concern.
> 
> JPC



I think that might be a red herring to an extent. The velocity at the filter outlets can be varied independently to the filter inlets, simply by differing the size/capacity and number of each respectively.

For example if you have 3000 litres per hour in through a single outlet and out through a single inlet, you’ll, you can decrease the outlet velocity by, for example, doubling the number of outlets, but the inlet uptake should still be the same if you kept that as a single inlet.

Now there is an argument for increasing the number of inlets to obtain more even distribution, since the distribution is achieved by both the outlets pushing water in a certain direction or pattern, and the inlets pulling the water in a certain direction.

I think if low velocity is the objective, then quite possibly the number of inlets needs to be increased so water isn’t drawn naturally to a single point in the tank.


----------



## jaypeecee (1 May 2020)

Wookii said:


> Let’s just assume we can choose any number, size, style and position of inlets and outlets as is necessary to achieve the design goal.



Hi @Wookii 

In order to ensure that we're 'singing from the same song-sheet' what _exactly_ is your design goal? It's not a 'low' velocity system, is it? Wouldn't it be more accurate to say an 'optimum' velocity system, whatever we deem to be 'optimum'?

JPC


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## jaypeecee (1 May 2020)

Wookii said:


> Now there is an argument for increasing the number of inlets to obtain more even distribution, since the distribution is achieved by both the outlets pushing water in a certain direction or pattern, and the inlets pulling the water in a certain direction.
> 
> I think if low velocity is the objective, then quite possibly the number of inlets needs to be increased so water isn’t drawn naturally to a single point in the tank.



Hi @Wookii 

The point that you are making above is what I had in mind when mentioning my single-inlet setup. Perhaps I should have spelled it out in more detail. The thing is that a single filter inlet can only draw in particles that are in very close vicinity. Multiple inlets should be more effective.

JPC


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## dw1305 (1 May 2020)

Hi all, 





sparkyweasel said:


> I can't access the full text at the moment, but it might be interesting to anyone who can.


I don't have access to this one either.

cheers Darrel


----------



## Wookii (1 May 2020)

jaypeecee said:


> Hi @Wookii
> 
> In order to ensure that we're 'singing from the same song-sheet' what _exactly_ is your design goal? It's not a 'low' velocity system, is it? Wouldn't it be more accurate to say an 'optimum' velocity system, whatever we deem to be 'optimum'?
> 
> JPC



No, low velocity is indeed the design goal - to encourage the most natural behaviour from the tank fauna, which I seem to observe when the flow velocity is zero (i.e. filter and skimmer are off).

Obviously we can’t have zero flow, as we need the filters biological filtration (to an extent - I appreciate less so in a heavily planted tank) and we need to distribute CO2 et al to the plants with no dead spots - i.e. sufficient distribution. 

So optimum distribution is a secondary design goal, albeit being counter the to the primary design goal, but the primary design goal is still achieving that optimum distribution with the lowest possible ‘velocity’.

The more I think about it, the more I think that as you reduce velocity, you more you need to increase turnover to compensate, so you are driving greater volumes of ever slower moving water around or along the tank.

In my own new tank which is relatively narrow to its length (1500 x 450 x 450) I’m thinking inlets at one end, outlets at the other - and achieving lowest velocity with sufficient distribution is dumping increased quantities of water at the outlet end via increased turnover, so the whole body of water is being slowly displaced by the slow moving mass of incoming water.

My other thought of course is that I’m just over thinking all this lol - but it’s an interesting theoretical exercise non-the-less.


----------



## kilnakorr (1 May 2020)

Wookii said:


> My other thought of course is that I’m just over thinking all this lol - but it’s an interesting theoretical exercise non-the-less.


I'm sure you are, but these discussions are how we learn and come up with new ideas.
Been following this thread closely, and just added spraybar today for a test. Have low turnover, but no dead spots as far as I can tell.
The spraybar isn't great looking but neither are powerheads. Otos and shrimps are far more active in the open areas now.


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## Wookii (1 May 2020)

kilnakorr said:


> I'm sure you are, but these discussions is how we learn and come up with new ideas.
> Been following this thread closely, and just added spraybar today for a test. Have low turnover, but no dead spots as far as I can tell.
> The spraybar isn't great looking but neither are powerheads. Otos and shrimps are far more active in the open areas now.



Great stuff, you’re about 10 steps ahead of me then - I think practical tests are the only real way to come up with a real design. How have you orientated the spray bar, and where is/are your inlet(s)?


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## kilnakorr (1 May 2020)

Wookii said:


> How have you orientated the spray bar, and where is/are your inlet(s)?


Spraybar is 'standard' full length at the back.
Inlet at back corner.
Using an older tank with drilled holes at bottom, so can't move inlet / outlet


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## alto (1 May 2020)

Wookii said:


> As an aside though, it would be interesting to understand why those tanks from those experienced aquarists achieve good algae free plant growth with minimal apparent velocity.


Thanks for the “experienced” accolade 

But I also had maybe 2-4x flow (I never checked) on my first tanks - OK the very first tank was one of those box kits (a surprise “present”) that needed filter and lighting upgrades so I just traded that out for another kit tank (not much else available in shops at the time) that delivered much better lighting, and visibly better flow (though far from high flow), and also had a much nicer “finish”

I knew absolutely nothing about fish (and never intended to get a fish tank) when I began, but I did garden - outside -
I am still a terrible indoor plant keeper 

And I began reading online and books - and a local aquarium shop owner was very interested in planted aquariums and had a copy of Takashi Amano Nature Aquarium World and other books for browsing (and the important Chair )

I did always do frequent 50% (& more) water changes - I was appalled by the concept of limited fresh water for _optimum_  fish care


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## alto (1 May 2020)

Double post


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## jaypeecee (2 May 2020)

Wookii said:


> ...the primary design goal is still achieving that optimum distribution with the lowest possible ‘velocity’.



Beautifully put! We're now on the same wavelength. 



Wookii said:


> I’m just over thinking all this...



No, I don't think (!) so. I suspect there may have been some people who, at the time, suggested that Thomas Edison was overthinking how to make a commercially-viable electric light. 

JPC


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## Emil. (7 May 2020)

I 100% agree that fish look more relaxed in the absence of flow. It would be great to have the best of both fauna and flora worlds.

One out of the box (read: stupid ) solution would be to have CO2  distributed to many tiny diffusers strategically placed underneath each non-easy plant. This brings many challenges: the amount of diffusers, the distribution itself and most annoyingly the clogging and maintenance.

Another idea: What about inline CO2 reactor and water raining down over the whole surface area?

Or! Outlet evenly “pipped” around the whole circumference at the bottom of the tank, gently spraying towards the centre, overflow on top. But would the fishies be okay with gentle but constant up flow? I assume it’s much easier for them to move forward than swim down.

I’m out of ideas for now. Please feel free to tear any/all of them down, I won’t be offended at all. Just trying to brainstorm, that’s all.


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## jaypeecee (7 May 2020)

Emil. said:


> I 100% agree that fish look more relaxed in the absence of flow.


Hi @Emil. 

I'm only stating the obvious here but it will depend on choice of fish species as to whether or not they prefer 'high' or 'low' flow.

JPC


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## Emil. (7 May 2020)

jaypeecee said:


> I'm only stating the obvious here but it will depend on choice of fish species as to whether or not they prefer 'high' or 'low' flow.



You're right, @jaypeecee . I should have worded it better. Same as the OP, I too have observed that my fish seem to be more relaxed and inquisitive of their surroundings with lower flow.


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## hypnogogia (7 May 2020)

Wookii said:


> I’ve even considered whether it would be possible to have pipe work under the substrate feeding sprinkler type head at various points (hidden from view by hardscape of course) allowing slow outflow across the bottom of the tank - but the more I think about that, the more it feels like a maintenance nightmare.
> 
> Anyone have any other ideas?



 I seem to remember a family friend having exactly that in cube in the eighties.  Lots of tiny siphons sticking out of the substrate connected via a network of tubes that all fed into a 16/22 tubes that ran to the filter.  Not sure if it was an eheim of Sicce set up.  I’m not sure how long it lasted before the under substrate tubes clogged up and they needed to dismantle the lot.


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## Wookii (7 May 2020)

Emil. said:


> I 100% agree that fish look more relaxed in the absence of flow. It would be great to have the best of both fauna and flora worlds.
> 
> One out of the box (read: stupid ) solution would be to have CO2  distributed to many tiny diffusers strategically placed underneath each non-easy plant. This brings many challenges: the amount of diffusers, the distribution itself and most annoyingly the clogging and maintenance.
> 
> ...



Some good ideas here, thanks for the input. The ‘tiny diffusers’ suggestion was along the similar lines I was thinking with under substrate pipe work and sprinkler heads at ‘strategic’ points. The maintenance is a major issue with anything plumbed under the substrate, and is something I’m concerned about.

The ‘rain’ idea is an interesting one, but I suspect it’d struggle getting the CO2 rich water back down to the substrate level, especially as the outlet water would be presumably running past heaters first and would be slightly warmer than the tank water - warm water rises, so it might stay towards the top of the tank. There is also the issue of aesthetics of course in a rimless tank without canopy.

Similar issue with the substrate level perimeter spray bars, I suspect the aesthetics would kill that one. Though a top to bottom distribution is interesting.

That brings me onto @foxfish’s previous experiment of a reverse undergravel filtration system - that sounds like a solid idea to distribute CO2 from bottom upwards. I just wonder if different substrate thicknesses or other irregularities could cause dead spots. @foxfish could you go into any mor detail on how that turned out?

Keep the ideas coming though, some good input there!


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## Wookii (7 May 2020)

jaypeecee said:


> Hi @Emil.
> 
> I'm only stating the obvious here but it will depend on choice of fish species as to whether or not they prefer 'high' or 'low' flow.
> 
> JPC





Emil. said:


> You're right, @jaypeecee . I should have worded it better. Same as the OP, I too have observed that my fish seem to be more relaxed and inquisitive of their surroundings with lower flow.



Good point, and a caveat I should have thought of making myself.

My observations are limited to very small number of species I keep in my tank. For the sake of completeness that includes Ember Tetras, Pygmy Corys and Chilli Rasbora.


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## Emil. (8 May 2020)

Wookii said:


> My observations are limited to very small number of species I keep in my tank. For the sake of completeness that includes Ember Tetras, Pygmy Corys and Chilli Rasbora.


What a coincidence, I have pygmies and embers too. I set up a low tech tank with a sponge filter for the pygmies and they seem very happy. Had the embers not been eating pygmy food all the time, I'd move them too.


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## Wookii (9 May 2020)

So whilst researching hardscape layouts for longer tanks I stumbled on a video by @George Farmer at the Interzoo show in 2018. The tank, designed by Jurijs Jutjajevs is 2400mm x 300mm x 300mm and has a very unique inflow/outflow design. Obviously in the case of this tank they wanted to create a very fast flowing tank like a small stream, and are pushing 100x turnover through the tank (about 22,000 litre per hour). However I wonder how well the design might translate to what we are discussed in this thread to the extent that the inlet and outlet are both at substrate level, so CO2 and nutrient rich water might more naturally flow over all areas (subject to hardscape exclusion) of the substrate from one end to the other. Other than the obvious loss of tank real estate at either end, the design is equipment free in tank. Obviously the inlet and outlet sizes (and hnec the loss of tank real estate) could be reduced a significant amount if say 10x-20x flow was targeted in the design instead.






You can see it working in the video here (6:25 onwards):



Also in a different video (below) of George's, but at the same event, there is an other unique inlet/outlet design. The outlet appears to just have a single hole in a piece of acrylic tube in one corner pushing up through the substrate, with an outlet of similar design in the opposite corner. This is an 1800mm tank.





That said, they do use a circulation pump on one corner, and the tank does appear to have a high amount of circular flow looking at the leaf movement in the video - but its an interesting idea non-the-less: Check it out (see from 3:35 onwards):


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## Emil. (15 May 2020)

Practicality aside, would air tight hood with CO2 only above the water surface work for CO2 distribution? Could the surface agitation in this scenario be delivering  enough CO2 to the water column? 🤔


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## Wookii (15 May 2020)

Emil. said:


> Practicality aside, would air tight hood with CO2 only above the water surface work for CO2 distribution? Could the surface agitation in this scenario be delivering  enough CO2 to the water column? 🤔



It's an interesting idea, but I think it might cause more issues than it solves. You still have to get the CO2 from the surface to the bottom of the tank, so you still have to implement strong flow/water velocity which is what we're trying to avoid in this design goal - otherwise I would assume you'd just end up with a thin layer of water at the top of the tank in equilibrium with the CO2 enriched air gap.

I also suspect that pumping the surface air gap with lots of CO2 would push out most of the oxygen, so you could end up with an issue of insufficient oxygen in the water column also.

I think an external reactor is always going to be the best option for efficient CO2 delivery, but the question is then how to deliver that CO2 enriched water to all the corners of the aquarium most efficiently, and with minimum velocity.


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## Zeus. (15 May 2020)

Emil. said:


> Practicality aside, would air tight hood with CO2 only above the water surface work for CO2 distribution? Could the surface agitation in this scenario be delivering enough CO2 to the water column? 🤔




So like a CO2 reactor - yes, but we also need O2 esp at night, so best to use a CO2 reactor then plants/livestock still get CO2 at night, plus gassing off at the waters surface helps maintain stable [CO2] and prevents the [CO2] from getting too  high. But as @Wookii points out we still need good flow 'Flow is King' in the supply of CO2 to our plants esp in tanks with high [CO2]


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## Hufsa (9 Jan 2021)

Im gonna bump this thread a bit and ask you @Wookii  what outlet/intake setup have you ended up with?

Ive been generally unhappy with, fidgeting and experimenting a lot with my filter outlet, most of my fish seem to enjoy the slower parts of the tank and I would like the same thing as was the goal in this thread.

Having a spray bar along the entire back of the tank served the plants well, but gives the fish some confusing swimming habits. 
Instead of swimming against the flow horizontally like in a river or a small stream, they swim against it vertically and it looks kinda strange. I dont know if it bothers them though.

Now I have the spray bar placed along the left side wall, with the intake in the back left. I quite like it, aside from the slightly unnatural zone in the midwater where the left leaving and right returning currents cancel each other out, it feels a bit more natural. 
The fish swim horizontally instead of surfing up and down the front glass, and I feel like it looks more comfortable for them. 
However I still think I may have too much velocity as my boraras swim against the glass right below the spray bar, and my pygmy corys always congregate in the area right in front of the filter intake. Its also kinda annoying to feed as the food gets blown away so easily. 
I want to make a custom spraybar for my tank width like I did for the back wall, but this time aiming for lower velocity. Im just waiting for some materials.

But I have also thought about getting flow going only one way, ie from the left to the right and not back again. This would not create the strange zone in the midwater.
My immediate thoughts are that the bottom left (below spraybar) and front right (opposite of intake) would be spots with less flow. 
I also worry that the velocity from the spray bar might have the water hit the right side glass at such a speed that it bounces off and starts going back left again, sort of missing the intake. But I have not tested this in practice. It may be possible to avoid this when designing the spraybar.

Who could have thought one could spend so much time thinking about some bits of plastic.


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## Aqua360 (9 Jan 2021)

Walstad?


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## Hufsa (9 Jan 2021)

Aqua360 said:


> Walstad?


What do you mean?


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## Aqua360 (9 Jan 2021)

Hufsa said:


> What do you mean?


Just suggesting if the OP likes the behaviours of fish etc in minimal flow, this could be a worthwhile avenue...
It doesn't however, answer the original question, I'll concede.


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## Hufsa (9 Jan 2021)

I didnt think Walstad had much to do with amounts of flow to be honest. I know at first she said no flow, but then later revised her method to include a small circulation pump, as no water movement was a bad idea. Thats the short of it as far as I understand.


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## foxfish (9 Jan 2021)

What size is your tank and just how much flow do you have? 
Are you using C02?


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## Hufsa (9 Jan 2021)

Tank is 180 liters, soon to be upgraded to 250 l. Filter is Ultramax 2000 which advertises 2000 lph (very theoretical). I heard real output is closer to 700-800 lph. No CO2 🙂


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## foxfish (9 Jan 2021)

Well you probably dont need anything like that amount of flow in a low tech tank although in 250lt your filter would be more suited .
A full lenth spray bar across  the back is probably the most gentle form of getting an even flow, ajusting the hole size and number will adjust the the flow effect and reduce any jetting there might be.
I am pleased you are concerned about you fish and excess flow might be an issue for some lake dwelling fish but adding some rocks or wood should offer calm areas.
I can recall a controversial chap on this form a few years back who insisted on using an amazing 50x flow rate as he considered this more natural for river dwelling fish  (piranhas i think) .


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## Wookii (9 Jan 2021)

Hufsa said:


> Im gonna bump this thread a bit and ask you @Wookii  what outlet/intake setup have you ended up with?
> 
> Ive been generally unhappy with, fidgeting and experimenting a lot with my filter outlet, most of my fish seem to enjoy the slower parts of the tank and I would like the same thing as was the goal in this thread.
> 
> ...



Hi mate,

No this thread was thinking about flow designs for my 1500 tank which I have had to put on hold as SWMBO wants to move house in the next couple of years, so I may as well wait rather than trying to move a filled tank.

I came to the general (but unproven) conclusion in my own mind that, in order to get good distribution (given it would be a CO2 injected tank) whilst reducing water velocity, I would need to trade velocity for volume.

What I mean by that, is imagine a slow flowing river. Say it’s going really slow, say 1m movement every 10 seconds. The water velocity is very slow, but volume of water being displaced is very high. So that is the principle I was going to try and adopt, distribution by displacement using a high volume of slow moving water.

Obviously we can’t easily replicate that kind of river movement in an aquarium exactly (it’d be about 72,000 litre per hour turnover on a 300 litre 1500mm tank, if my calculations are correct) but I was planning on doing something similar.

My plan was to use a acrylic pipe as a spray bar at one end - similar to what you are doing now - but with the exit point to the sump at the other end so flow is in a linear direction. The spray pipe would be around 30-50mm OD, with a variety of large holes cut in it - I planned to have the spray pipe threaded to screw onto the pump inlet bulkhead in the tank, so it could easily be replaced and I could try different patterns and designs.

I then planned to use one (or maybe two) Ecotech Marine Vectra L2 pump(s), rated at 11,500 lph, to push the water through it. I would enlarge to holes sufficiently such that the velocity through them is as gentle as possible. 

The basic principle in my mind was to dump 10,000-20,000 litres per hour in one end of the tank, so it displaces all the water all the way down the tank, but in a way that has low water velocity. 

Obvious this is all just planning stage stuff - it might not be physically possible - the sump might not be able to handle that flow, I might not be able to sufficiently reduce the velocity of the water exiting the spray tube, the volume turnover might still not be enough to avoid dead spots and achieve complete regular displacement of all the water in every area of the tank. Lots on unknowns but I plan to give it a through go and test one day.


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## Paul Kettless (9 Jan 2021)

For once this is a subject that I may actually be able to have some input with. After keeping reef tanks for many years, eliminating dead spots, distributing nutrients via dosing and getting gentle flow (especially for soft corals, they would close up if the flow was too strong) we would use a combination of a sump tank, and wavemakers on a controller.

The weir generally would be in the middle of the tank and not a corner, I outlet and 2 intakes with one pointed left and the other pointed right giving two circular motions.  I found it impossible to eliminate dead spots in a marine tank with such volumes of live rock, unless you used wavemakers. The really serious guys would drill there tanks multiple times all over it with directional bulkeads and use a huge water pump to split the flow equally.  This off course involves lots of pipework and a poweful non emersed pump.  It mentioned previously in this thread by someone, and I cant remember who sorry! That they use 2 powerheads on a controller and vary the speed of the pumps at different times of the day.

This was exactly the process that 90-95 percent of reefkeepers would use to distribute good flow (not fast unless you wanted that off course)  The wavemakers I had were x 4 and the program would alternate the pumps at various intervals, and power.  This would vary during the day/night, at some points the pumps may only be having 2 working at 10 percent. I would have them gentle over the early mornings, ramped accross the main lighting period and then reduced again considerablyat night.  You would definitely see a difference in the fauna behaviour when the flow was less, well apart fron the tangs they would sulk.

Asthetically not the most attractive things, and the ones that are demand a heavy cost.  Although It seems the issue we have here is that Aquascapers want clean, almost clinical lines in ther tanks and rightly so for obvious reasons, but sometimes to achieve a goal a compromise has to be made.  Im amazed that more aquascapers dont use wavemakers/powerheads more in there aquariums.  After all "wavemaker" sales pitch is just a pump that is fully controllable in speed, flow just moves water at whatever rate/direction you want it to.  It worth mentioning here, that I am not talking about high flow rates here, but the flow that youn want to achieve.

Edited typos#


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## Zeus. (9 Jan 2021)

Hufsa said:


> Now I have the spray bar placed along the left side wall, with the intake in the back left. I quite like it, aside from the slightly unnatural zone in the midwater where the left leaving and right returning currents cancel each other out, it feels a bit more natural.



Having had twin spraybars in my 500l at either end of tank I can feel your pain, and maintenance was a real PITA. Then to having twin Maxspect 330 with controller and 9000l/h output life as become so easy. 
It does mean when gyres on full I have a theoretical output of 18000l/h plus the Fluval FX6 so about x36 to x40. Fish have to choose their swim areas to suit. I was also concerd that going from  zero to full power would send a wave over the end of tank, no such issues as you can control how fast it get to full speed. Only use full power when doing maintenance, have them changing every 5mins from one  @ 50% and other @20% and hourly 5mins worth of 1min @70% and 20%, run this schedule form CO2 on till lights off. At night I just have one on at a time for about an hour, as it allows leaves to fall off them and cleanup crew to clean them


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## Paul Kettless (9 Jan 2021)

Zeus. said:


> Only use full power when doing maintenance, have them changing every 5mins from one @ 50% and other @20% and hourly 5mins worth of 1min @70% and 20%



Very good point and I would also do this on a water change day for a short period just to get as much detritus in the water column for maintenance and water change.


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## Zeus. (9 Jan 2021)

Paul Kettless said:


> Very good point and I would also do this on a water change day for a short period just to get as much detritus in the water column for maintenance and water change.



Yes thats what I do and turkey blast the substrate then just clean the filter media after an hour or so after a WC


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## Hufsa (9 Jan 2021)

Wookii said:


> ..so I may as well wait rather than trying to move a filled tank.
> 
> ..Obviously we can’t easily replicate that kind of river movement in an aquarium exactly (it’d be about 72,000 litre per hour turnover on a 300 litre 1500mm tank, if my calculations are correct) but I was planning on doing something similar.
> 
> ..Lots on unknowns but I plan to give it a through go and test one day.



Ah yeah that makes sense. Those sure are some dizzying numbers. It will be interesting to read if/when you ever end up testing this. Hope you will share it with the forum 



Paul Kettless said:


> ..You would definitely see a difference in the fauna behaviour when the flow was less, well apart fron the tangs they would sulk.



I swapped out the spraybar I had in for one with even bigger holes and so far the results are positive with the fish. They are a bit more all over the place now. So that makes me confident this is something I can do to increase their comfort, and not something ive just been imagining. It may have slightly too many holes this one, but again a custom one I can make perfectly tuned. Obviously perfect in this sense is a totally nebulous point of compromise between the fish and the plants. I keep plants for the benefit of the fish, which makes things slightly easier.



Zeus. said:


> ..twin Maxspect 330 with controller and 9000l/h output life as become so easy.
> ..It does mean when gyres on full I have a theoretical output of 18000l/h plus the Fluval FX6 so about x36 to x40. At night I just have one on at a time for about an hour, as it allows leaves to fall off them and cleanup crew to clean them



The gyre pumps sure are innovative, if I ever make a river tank I will probably use them for flow. 
I suspect they would be overkill for this tank though, it feels a little bit like buying a racecar that you use only for dropping grandma off to bingo night. 
How are the gyre pumps protected, are they like most wavemakers that they have a guard around them, but the guard is dimensioned mostly for larger fish?
Would covering them in mesh/netting impair their function?
I have itsy bitsy fish and a lot of fry so I have to safeguard everything with very fine mesh, otherwise things get tragic. Its a pain in the a 😅


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## Zeus. (9 Jan 2021)

Hufsa said:


> I suspect they would be overkill for this tank though, it feels a little bit like buying a racecar that you use only for dropping grandma off to bingo night.



Whats the top speed of the car you drive and how often you you drive it that fast ? Its the same with the gyres. As for the fish shrimp well I have a rule of no fish bigger than 3cm when fully grow and have had had no known issues, I sure some young shrimp have not survived the vertex of death whilst other baby shrimp just get eaten by the fish. For Beta fish I would keep well clear as well as some other fish as well. The output can be set in 10% steps.


Hufsa said:


> How are the gyre pumps protected,



I use the mesh guards which came with the gyres which are two years old and still good. Probably does affect their output but plenty of head room


----------



## Wookii (9 Jan 2021)

Paul Kettless said:


> For once this is a subject that I may actually be able to have some input with. After keeping reef tanks for many years, eliminating dead spots, distributing nutrients via dosing and getting gentle flow (especially for soft corals, they would close up if the flow was too strong) we would use a combination of a sump tank, and wavemakers on a controller.
> 
> The weir generally would be in the middle of the tank and not a corner, I outlet and 2 intakes with one pointed left and the other pointed right giving two circular motions.  I found it impossible to eliminate dead spots in a marine tank with such volumes of live rock, unless you used wavemakers. The really serious guys would drill there tanks multiple times all over it with directional bulkeads and use a huge water pump to split the flow equally.  This off course involves lots of pipework and a poweful non emersed pump.  It mentioned previously in this thread by someone, and I cant remember who sorry! That they use 2 powerheads on a controller and vary the speed of the pumps at different times of the day.
> 
> ...




To be fair I use an AI Nero 3 power head currently for additional flow on my current 100 litre - it’s a great bit of kit, I have it on a slow pulse mode to vary the intensity of the flow for a more natural ebb and flow effect.

That said though, even though the Nero 3 has a nice wide spray pattern the water velocity is still a lot more than I’d like it to be to get leaf movement at the opposite end of the flow direction.

The flow in the majority of reef tanks that I have seen is far more than we’d have in a planted tank, and miles more than I was shooting for  when I was trying to come up with the design in this thread.

To be honest I’m quite possibly asking for the moon on a stick achieving even distribution with very low water velocity on a high tech tank.

The real world answer is probably to remove the requirement, or at least lower the importance, of good distribution, which kind of leads you down the path of low energy/low light. To be fair, that’s the way my preferences are starting to lean anyway, as I fancy a more habitat style layout for this tank when it eventually gets set up.


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## Andy Pierce (9 Jan 2021)

Emil. said:


> Practicality aside, would air tight hood with CO2 only above the water surface work for CO2 distribution? Could the surface agitation in this scenario be delivering enough CO2 to the water column? 🤔


I tried CO2 gas injected into the air pump airstream so the CO2 was only in the main bubble stream and not through any type of atomiser/diffuser in my closed top tank and that seemed to work just fine to get CO2 into the water column as measured by a drop checker: CO2 diffuser, Fireplace aquarium.  The hood doesn't need to be totally air tight, just sufficiently closed to not let air currents rapidly sweep away the CO2 enriched air layered on top of the water.  I wouldn't recommend a layer of pure CO2 on top of the water but a CO2-enriched air-CO2 mixture seems to get the job done.  Others have noticed similar with open topped tanks in rooms that have enriched CO2 concentrations in the entire room (because the room has poor ventilation and is occupied by breathing people) e.g.: Concentrations of CO2 in the home - Reef Central Online Community


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## Andy Pierce (10 Jan 2021)

Emil. said:


> I 100% agree that fish look more relaxed in the absence of flow. It would be great to have the best of both fauna and flora worlds.


I did a little mini experiment last light looking at the effects of flow on fish behaviour.  Link to video:  Fish behaviour:  water flow vs. lighting, Fireplace aquarium.  I too thought flow was having a big influence on fish behaviour but now I'm much less convinced - my fish at least seem completely unperturbed by greatly increased water flow.  What DOES have a huge influence though is lighting.  The effect of the flow is subtle but light influences are immediate and dramatic.  I noticed different behaviour in the process of transitioning from a low tech to high tech setup which at the time I attributed to installation of a powerhead, but now I'm thinking it was actually the significantly upgraded lighting that was the main driver.


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## Paul Kettless (10 Jan 2021)

Andy Pierce said:


> I did a little mini experiment last light looking at the effects of flow on fish behaviour.  Link to video:  Fish behaviour:  water flow vs. lighting, Fireplace aquarium.  I too thought flow was having a big influence on fish behaviour but now I'm much less convinced - my fish at least seem completely unperturbed by greatly increased water flow.  What DOES have a huge influence though is lighting.  The effect of the flow is subtle but light influences are immediate and dramatic.  I noticed different behaviour in the process of transitioning from a low tech to high tech setup which at the time I attributed to installation of a powerhead, but now I'm thinking it was actually the significantly upgraded lighting that was the main driver.


No question, I just watched all of the video, and the nothing to everything startled the fish, a gradual increase in light is the ideal way. as this video only showed a minute of activity after the light is on to do you notice with time that the fish come from under the plants and swim more openly?


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## Hufsa (10 Jan 2021)

Andy Pierce said:


> but light influences are immediate and dramatic.


What an interesting video 😮 I agree that really was a dramatic change, the light does look super bright but that may be influenced by the video capture I suppose. In respect to your specific situation I would wonder if its possible to reduce your lighting a bit?

There may be some difference in requirements from fish to fish, well it seems obvious when I put it this way but a "tetra" is not a "tetra" in all cases. Or what I mean is schooling fish may have very different requirements. Both me and @Wookii have Boraras, which come from fairly still blackwaters. At least all videos ive seen of Boraras sp. in nature has been in little pools with minimal water movement. Not completely stagnant but minimal water movement. So its possible that I should aim for a lower water velocity than you might get away with having your active Rummynoses.

Its hard to write this without sounding rude, but in regards to the contibution by @reefkeeper1 , I would much rather be accused of caring too much than caring too little. Do I have a tendency to overthink? Definitely, but I think its worth it. I wish you could find a better way to phrase some things, as the good points you make get lost in the somewhat abrasive way you present it 🙂

This thread may be morphing into a "how to increase our fishes' comfort level", but I think thats great. I get the impression sometimes that fish are added almost as an afterthought to aquascapes, and that seems like a shame to me. Their needs should come first and plants should come second. But I think with some experimenting it should be possible to have comfortable fish while still facilitating good plant growth. Good plant growth is good for the stability of the tank and therefore the fish, after all.


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## Andy Pierce (10 Jan 2021)

Paul Kettless said:


> No question, I just watched all of the video, and the nothing to everything startled the fish, a gradual increase in light is the ideal way. as this video only showed a minute of activity after the light is on to do you notice with time that the fish come from under the plants and swim more openly?


Time after the lights come on, even hours later, doesn't really seem to change their behaviour; as long as the light is on they stay towards the bottom.  There are photos rather than video here: Lights on – lights off!, Fireplace aquarium where in the "lights on" photo the light has been on for over 5 hours already. The fish aren't right down under the plants but they are down in that bottom right quandrant and the photo is reasonably representative of their general lights-on behaviour.  The "lights off" photo is 50 minutes after the lights have been turned off, which doesn't look obviously different to the video where the lights have been off for hours.  It would be interesting to see whether a gradual increase/decrease in light levels makes a difference, but my set-up isn't equipped to do that.  If someone else wants to put something together I'd be really interested in seeing it. 

That being said, I was mainly trying to determine whether flow was changing the fish's behaviour and I'm pretty confident now that it is not, at least not with these fish (rummy nosed tetras, 5-banded barbs and otocinclus catfish) in my setup.


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## Emil. (10 Jan 2021)

Andy Pierce said:


> I was mainly trying to determine whether flow was changing the fish's behaviour and I'm pretty confident now that it is not


Excellent video, thanks Andy! I don't think light and flow are mutually exclusive in hiding the fish, however. Imho, they hide from light to be safe and they hide from high flow to rest their fins. It's definitely good to know that light plays a factor too.


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## Emil. (10 Jan 2021)

Paul Kettless said:


> Im amazed that more aquascapers dont use wavemakers/powerheads more in there aquariums.  After all "wavemaker" sales pitch is just a pump that is fully controllable in speed


Paul, that's brilliant.  Provided that wavemaker can distribute ferts & co2 adequately every day, I like the idea of having just sponge filter as a filtration. Super easy maintenance, plenty of oxygen all the time and large rest intervals for the fish when the wavemaker is off. The only downside is that the diffuser and heater would need to go back in the tank but I bet it can all be hidden. Has anyone tried this setup?


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## Paul Kettless (10 Jan 2021)

Emil. said:


> Paul, that's brilliant.  Provided that wavemaker can distribute ferts & co2 adequately every day, I like the idea of having just sponge filter as a filtration. Super easy maintenance, plenty of oxygen all the time and large rest intervals for the fish when the wavemaker is off. The only downside is that the diffuser and heater would need to go back in the tank but I bet it can all be hidden. Has anyone tried this setup?


I cant see no reason why it wouldnt all wavemakers are designed for is to assimulate current and help you eliminate dead spots.  going back to a reef tank again, the pumps would be working harder at the times when the dosing machine was working to try and evenly distribute around the tank. When lights out the pumps would slow considerably, no different to how you would work lights, co2 and ferts i guess.


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## Andy Pierce (15 Jan 2021)

Andy Pierce said:


> I did a little mini experiment last light looking at the effects of flow on fish behaviour.  Link to video:  Fish behaviour:  water flow vs. lighting, Fireplace aquarium.


I followed up with a video of what happens when the light turns off at the end of the day:  Fish behaviour: water flow vs. lighting – pt 2, Fireplace aquarium.  It is largely the reverse of what happens when the lights turn on except slightly more gradual where the fish that swim at the bottom come back up above the midground plants when the light goes off.  Same story with the two different powerhead speeds as before with very little effect on how the fish behave.  I'm pretty convinced it is the actual state of the light rather than the abruptness of the transition that matters.  Anyone else see an obvious effect of lighting on fish behaviour?  It may be simply that in a larger tank there's less of an effect.


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## john dory (16 Jan 2021)

Yes,certainly.
Watching my fish,as we speak(lights off)..in well over 10 times(stated)flow.
Probably nearer 20x
Just milling around in the tops of the stems.


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## john dory (16 Jan 2021)

Regarding flow patterns 

Sent across the front length of the tank,by the time it's bounced off the far end..forced down..and then back across the rear.
There's only enough to gently rock my stems.

That's a 600 biomaster coupled with a powerhead of similar output,in a 1 metre long tank,containing 150l of water.


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## Sammy Islam (16 Jan 2021)

Andy Pierce said:


> I followed up with a video of what happens when the light turns off at the end of the day:  Fish behaviour: water flow vs. lighting – pt 2, Fireplace aquarium.  It is largely the reverse of what happens when the lights turn on except slightly more gradual where the fish that swim at the bottom come back up above the midground plants when the light goes off.  Same story with the two different powerhead speeds as before with very little effect on how the fish behave.  I'm pretty convinced it is the actual state of the light rather than the abruptness of the transition that matters.  Anyone else see an obvious effect of lighting on fish behaviour?  It may be simply that in a larger tank there's less of an effect.


I have noticed that my ember tetras become "playful" and "adventurous"  when my lights start ramping down. During lights on they are pretty stationary chilling in the bottom 3rd of the tank. After lights out they "sleep" in the top 3rd of the tank.


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## jaypeecee (15 Jun 2022)

Wookii said:


> I’ve even considered whether it would be possible to have pipe work under the substrate feeding sprinkler type head at various points (hidden from view by hardscape of course) allowing slow outflow across the bottom of the tank...


Hi @Wookii 

I remember having had that very discussion with you what must have been a couple of years ago.

JPC


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## Wookii (15 Jun 2022)

jaypeecee said:


> Hi @Wookii
> 
> I remember having had that very discussion with you what must have been a couple of years ago.
> 
> JPC



Well that line you've just quoted is from 2 years ago John 😂


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## hwscot (16 Jun 2022)

Late to this. My dream setup is a long stream-like tank, relatively wide and shallow. I came across the thread just the other day. I've been playing around with the idea of using a water blade to deliver flow into the tank, which from reading this thread, would be my alternative to a spray bar set up with large holes.
Part of my thinking comes from having had a large garden pond (before vandals made it non-viable, sadly) with the traditional top pond and a waterfall.
Instinctively the blade seems to me more natural in appearance than a spray bar, and a more uniform width of flow (the width of the stream, in effect) likely to give more of the effect of a large volume of water moving steadily down the length of the tank.
A weir as the outflow from the tank would be the natural other end of the stream. And I guess, in effect, the blade is not so different, in terms of flow 'shape', from a weir, but potentially simpler to manage if it simply connects to the pipework from the filter or pump. Blades come with either a rear or base input to the box.
Apparently a blade needs c. 1000 lph per ten cm width of blade to get a decent flow, so a blade say 20 or 30 cm wide on a tank of, say, 300 litres, doesn't sound so unreasonable. Lots of issues with the 'plunge pool' effect on substrate etc. but my notion was to have the lip of the blade only, say, 10cm above the water surface. Noise migh be an issue for some people, although possibly not much more than a large HOB. And I like the noise anyway. (the waterfall helped mask noise from a nearby road, and I find it relaxing).
Has anyone seen this tried? I'm guessing there must be tanks with a weir as input at one end and another as output at the other end; they would be interesting to look at while mulling all this over.


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## jaypeecee (17 Jun 2022)

hwscot said:


> Has anyone seen this tried? I'm guessing there must be tanks with a weir as input at one end and another as output at the other end; they would be interesting to look at while mulling all this over.


Hi @hwscot 

I suggest that you take a look at so-called 'river tanks'. This is a suggested layout:









						The secret to setting up a better river aquarium
					






					www.practicalfishkeeping.co.uk
				




One possible candidate fish for such a setup is one of my favourite fish - the Hillstream Loach - an example of which you'll find here:









						Hillstream Loach - Habitat, Care, Feeding, Tank Size, Breeding - AquariumNexus
					

Fish and other water creatures survive in a range of environmental conditions provided they are habitable. Being a hobby aquarist means that the animals you choose for your tank will be easy to keep and will thrive, provided you have the right tank conditions for them. One of the common options...




					www.aquariumnexus.com
				




And, here's some reading material:









						Gastromyzon punctulatus summary page
					





					www.fishbase.de
				









						Sewellia lineolata – Tiger Hillstream Loach (Balitora lineolata, Sewellia songboensis) — Seriously Fish
					






					www.seriouslyfish.com
				




Note the flow rate of water in the natural habitat for hillstream loach, i.e, > 1 meter per second!!

Just thought this might be of general interest.

JPC


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## Garuf (17 Jun 2022)

It’s my understanding a lot of the bigger plecs are from insanely high water speeds too.


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## Wookii (17 Jun 2022)

hwscot said:


> Late to this. My dream setup is a long stream-like tank, relatively wide and shallow. I came across the thread just the other day. I've been playing around with the idea of using a water blade to deliver flow into the tank, which from reading this thread, would be my alternative to a spray bar set up with large holes.
> Part of my thinking comes from having had a large garden pond (before vandals made it non-viable, sadly) with the traditional top pond and a waterfall.
> Instinctively the blade seems to me more natural in appearance than a spray bar, and a more uniform width of flow (the width of the stream, in effect) likely to give more of the effect of a large volume of water moving steadily down the length of the tank.
> A weir as the outflow from the tank would be the natural other end of the stream. And I guess, in effect, the blade is not so different, in terms of flow 'shape', from a weir, but potentially simpler to manage if it simply connects to the pipework from the filter or pump. Blades come with either a rear or base input to the box.
> ...



There are quite a lot of River/Stream tanks out there of different designs. The one in my post #60 in this thread is one of the best, and cleanest designs I've seen (20,000 lph):

(Time stamp 06:25 onwards)



In this video with Jurijs Jutjajevs, you can see a lot more of the technical construction etc:



Same tank design (could even be the exact same tank) shown here, and looks really nice:



There is also this tank (referenced in the above video also), that actually uses a sloping tank to help achieve the high flow:



More details also at the start of Georges video here:


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## Conort2 (17 Jun 2022)

Garuf said:


> It’s my understanding a lot of the bigger plecs are from insanely high water speeds too.


Most l numbers love high flow, even the smaller hypancistrus, peckoltia etc thrive with it. Corydoras too, many species spawn directly in the flow of power heads.


Wookii said:


> There are quite a lot of River/Stream tanks out there of different designs. The one in my post #60 in this thread is one of the best, and cleanest designs I've seen (20,000 lph):
> 
> (Time stamp 06:25 onwards)
> 
> ...



Love the panta rhei tanks, definitely a if I win the lottery type set up though!


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## hwscot (17 Jun 2022)

Wookii said:


> There are quite a lot of River/Stream tanks out there of different designs. The one in my post #60 in this thread is one of the best, and cleanest designs I've seen (20,000 lph):


Saw that in the earlier post .. it's stunning. Really useful to have a bit more information about how it works.


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## Wookii (18 Jun 2022)

hwscot said:


> Saw that in the earlier post .. it's stunning. Really useful to have a bit more information about how it works.



It’s an amazingly simple design when you see it - and I can’t believe they get all that flow with just a single Gyre style flow pump. 20,000 LPH isn’t even the biggest of those style of pumps - as @Conort2 says, if I won the lottery there’d be a nice 3 or 4 metre river tank like that in the new millionaires pad!


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## Garuf (18 Jun 2022)

If I won the lottery I’d have a 2-3 metre sand bar shallow tank for corydoras.🤔


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