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

[Zeus.]

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

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.

 

[Wookii]

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.

 

[Zeus.]

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

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

 

[kilnakorr]

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.

 

[jaypeecee]

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

 

[jaypeecee]

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

 

[Wookii]

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.

 

[jaypeecee]

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

 

[Wookii]

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/

 

[jaypeecee]

Hi @Wookii

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

JPC

 

[Wookii]

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.

 

[jaypeecee]

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

 

[Wookii]

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

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.

 

[jaypeecee]

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

 

[Zeus.]

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.

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.

 

[Wookii]

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.

 

[kilnakorr]

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.

 

[jaypeecee]

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

 

[sparkyweasel]

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.

 

[jaypeecee]

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