# Another flow question



## Frenchi (30 Nov 2014)

Hi ppl
I have a few dead spots in my 250 litre tank. I have 2 x external filters one of them runs with the co2 returning to tank via spray bar pointing to front of tank,  the other is on a spray bar above the other helping the flow of the co2 along .. 
My intakes are both at the rear at either end of the tank. 
Do you guys know of another/ better way I could do this to get the best from the flow?

Cheers 

Mick


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## foxfish (30 Nov 2014)

The format is sound but much depends on the spray bar efficiency i.e. their overall length, hole  placement, size & number & of course the pumps performance under pressure?


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## Frenchi (30 Nov 2014)

Well if I'm honest the flow isn't fantastic but there is slight movement on most of the leaves but not all.. I'm not happy with it really ... I have the aquaone aquis 1200 which is 1200 lph and the aquis 1050 1000 lph .. 
I use 1 and half lengths of spray bar on each filter the standard aquaone bars.. But I have blocked a couple of holes where my wood goes up in front of it..


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## Frenchi (30 Nov 2014)

Would wave makers help at either end or should I be trying to create a one way type of flow?


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## paul2 (30 Nov 2014)

what if you removed some filter media from each filter ,would this help the flow?


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## Frenchi (30 Nov 2014)

paul2 said:


> what if you removed some filter media from each filter ,would this help the flow?


I did think about that as on top of each filter I have the White floss on top of fine foam .. The filters are a good few year old now and the media is even older so maybe I will try removing the fine foam and floss and replace with course foam or even japp Matt


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## dw1305 (1 Dec 2014)

Hi all, 





Frenchi said:


> I did think about that as on top of each filter I have the White floss on top of fine foam .. The filters are a good few year old now and the media is even older so maybe I will try removing the fine foam and floss and replace with course foam or even japp Matt


I'd chuck both the floss and the fine foam out, and replace them with coarse (PPI10) sponge. I don't like any fine mechanical media in the filters, it clogs really easily, reduces flow and potentially leads to problems with de-oxygenation of the water in the filter (less of problem for us than non-planted tank people).

If you can hide it in the tank I prefer a coarse (PPI10) or medium sponge (PPI20/PPI25) on the filter intake. This has the advantage of being really quick and easy to clean. 

I tend to use either the black 12" x 4" x 4" part drilled sponge blocks that Koi places sell cut to size, or <"DIY them to the size I want from foam sheet">. 

cheers Darrel


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## Frenchi (1 Dec 2014)

Thanks Darrel, that does make sense really .. I done that with my other tank but left the fine foams in too.. It's just something I've always done, time for a change I think.. I've loads of sponge from the pond so I'll give it a go. I might  even try a bit of jap matting it works a treat in pond filters 

Thanks


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## dw1305 (1 Dec 2014)

Hi all, 





Frenchi said:


> .. I done that with my other tank but left the fine foams in too.. It's just something I've always done, time for a change I think.. I've loads of sponge from the pond so I'll give it a go. I might  even try a bit of jap matting it works a treat in pond filters


 The sponge I really like is the stiff German Poret foam, but it is quite difficult to get in the UK. <"Swiss Tropicals"> sell it in the USA. 




 

cheers Darrel


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## Frenchi (1 Dec 2014)

I'll have a search around and see what I can find .. I have lifted my filters up in the cabinet 4" each so that should help a little too.. Every little helps as they say


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## Jose (1 Dec 2014)

Does anyone know the effects of foam pore size effect on bacteria colonization? I dont think there is info on this out there. Its quite a simple experiment to carry out really. Although it might take quite some time and two tanks are needed. Sorry to deviate the thread.


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## Frenchi (1 Dec 2014)

I'd say the courser the better really .. Well that's how it works on the pond anyway.. Obviously not too course .. Finer sponges are mechanical more than anything.. Most of my filters contain k1 media and ceramic.. The use of finer media is more to polish the water


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## Jose (1 Dec 2014)

Frenchi said:


> I'd say the courser the better really .. Well that's how it works on the pond anyway.. Obviously not too course .. Finer sponges are mechanical more than anything.. Most of my filters contain k1 media and ceramic.. The use of finer media is more to polish the water


Mmm Ok. But maybe it also has something to do with the length of the sponge, in other words, how much the water has to travel through it. For example, in my nano the sponge is only 2 inches thick, although quite long. So for this 2 inches I think its better to have a finer(middle ground) sponge so that it doesnt let things go through it too easily. Any thoughts?


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## Frenchi (1 Dec 2014)

You could always cut it in half and replace the other half with k1 or ceramic in a net .. I use a hair net but you can buy media bags with draw string ..


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## dw1305 (3 Dec 2014)

Hi all, 





Jose said:


> So for this 2 inches I think its better to have a finer(middle ground) sponge so that it doesnt let things go through it too easily. Any thoughts?


I'm with "Frenchi". I like a coarser sponge and filter media that doesn't inhibit flow too much. Even with smaller internal filters I wouldn't go finer than PPI25. 

If you start looking at the actual volume of bacteria you need it is relatively small, and usually what limits nitrification isn't pore space, but oxygen. This is why waste water scientists are interested in Biochemical Oxygen Demand (BOD) as the measure of pollution, rather than just the volume of the filtration system.

My suspicion would be that in nearly all filters not all the potential sites for nitrification are occupied, mainly because the water is de-oxygenated before it reaches them. 

Some people have even suggested that this is an advantage because anaerobic de-nitrication of NO3 can occur in the deeper pore spaces of sintered glass or fine sponge, but lets just say I'm deeply dubious whether this is a good idea in most filtration systems. 

An exception I would make would be for wet and dry trickle filters and HMFs, this is because they have large gas exchange surfaces (in contact with atmospheric oxygen in the case of the wet and dry, and atmospheric oxygen at the top and oxygenated tank water along the sides in the case of the HMF). A large gas exchange surface allows CO2 to out-gas and O2 to diffuse in along their respective diffusion gradients.  

In the case of an enclosed filter medium (like a canister filter) the oxygen carried into the filter can't be replenished from the water column while it is inside the filter. If flow through the filter is slowed by fine media, or a lot of organic debris from using your filter as a syphon, then the water will become de-oxygenated and the volume of the filter material becomes irrelevant. In this scenario some denitrification of NO3 may occur, but the real problem is that an increase in the bioload, or further slow in flow speed, may lead to ammonia passing through the filter and then accumulating in the tank water with disastrous results.

If you have plants and a substrate you have "_belts and braces_", but if you are entirely dependent upon the filter you are into a positive feedback loop of:

lower oxygen levels > increased ammonia > fish death > lower oxygen levels > increased ammonia > fish death etc.

cheers Darrel


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## Jose (3 Dec 2014)

Very interesting topic. Ok, so..coarse media is the preferred one here. But what about flow? Is more flow better. I mean not for oxygenation (suppose we have good O2 levels), but the flow going through the media. I was once told by an old school hobbyist that bacteria were more active when the flow was over 3 times the aquarium volume per hour and also when  it was under another value which I cant remember. Is this just one more myth? I believe it might be. If you think of it some filters have more flow going through the pores. Maybe we do need to determine our foam section surface in order to have the ideal flow through the pores? Maybe Im overthinking it now.


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## Frenchi (3 Dec 2014)

We actually do not need any foam really but it's best to have a bit before the either k1 or ceramics to prevent build up of solid waste plant matter etc .. Bacteria colony in the filter media should be enough to break down fish waste before it hits the tank again .. In my pond I have brushes that collect big waste and that's it the rest is jap Matting, k1 media and Alfa grog .. It's the same for any filter.. It's always best if filter media can move around slightly too to prevent any heavy build up of solids .. 
Hope I made sense of that I'm not good with thoughts into words ...


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## Frenchi (3 Dec 2014)

This is the bottom of my pond nearly 5ft deep .. My filter is mainly k1 media no sponges at all 




Taken just now
Edit:: sorry there is some japp matting in there


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## dw1305 (3 Dec 2014)

Hi all,





Jose said:


> But what about flow? Is more flow better. I mean not for oxygenation (suppose we have good O2 levels), but the flow going through the media. I was once told by an old school hobbyist that bacteria were more active when the flow was over 3 times the aquarium volume per hour and also when it was under another value which I cant remember. Is this just one more myth? I believe it might be. If you think of it some filters have more flow going through the pores. Maybe we do need to determine our foam section surface in order to have the ideal flow through the pores?


 I think it is a myth, there must be a maximum flow velocity that inhibits floc formation, but I'd be surprised if any of us get anywhere near it.

If you think about filter hoses, they clog will bacteria and algae even thought the water is exhibiting laminar flow through them at high speed.  Once the water is in the filter, flow will become turbulent and there will be areas of restricted flow, reversed flow and even stationary water.  

Optimal slow flow isn't an argument that holds water, unless you are interested in maintaining a balance between aerobic and anaerobic, to allow for de-nitrification of NO3 and out-gassing of N2.  

I'm not going to go there, if any-one is interested in it as a discussion there are linked threads in: <"Fish/shrimp Room project" >.

We can't measure either BOD or dissolved oxygen outside of the lab., but there is plenty of literature about them from aquaculture and waste water treatment.

All you have to do is extrapolate to the tank/fish/plants/filter/substrate system as a scaled down sewerage plant, with <"vertical flow constructed wetland">, where we are only dealing with lightly polluted effluent.  It isn't a particularly attractive scenario, but it covers all the subject area fairly comprehensively.

cheers Darrel


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## parotet (3 Dec 2014)

Love the last link you included in your post Darrel... Lots of ingesting info!

Jordi


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## foxfish (3 Dec 2014)

Trickle filters are so easy to construct but really need to be above the tank (or sump) which obviously don't fit in with the majority of planted tank designs.
However a simple Tupperwear box & a small power head  will outperform all but the biggest of canister filters!
Back in the 90s I spent an age developing a pressurised   tickle filter that could be placed below the tank & in fact a similar design became quite popular in the mid 90s especially for reef keepers without a sump.


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