# Circulation? Low flow? Planted tank with a betta...



## BanditCoaxx (25 Nov 2020)

So having observed my tank for a while it looks although I'm not getting a great deal of circulation, I'm using an Aqua Flow 100, which is apparently 200lph, from what I can gather not nearly enough for a planted tank but I also have a Betta in there. My filter is placed close to the substrate with the outlet pointing the length of the tank. Being so low I'm sure this is only moving part of the water in the bottom, and along with several plants being in the way, the right side doesn't see a lot of movement. So whilst trucking around this morning I thought of a potential solution; please excuse the child like drawing I have fat thumbs.

Purple - Internal Filter
Red - Heater
Green - Plants
Blue - Spray bar from amazon?

The spray bar I would attach just under the surface across the width/depth of the tank to create circulation with the yellow arrow?

Anybody else have any suggestions?

My other thought was to get a pump for the other side but I was thinking that would also just circulate the bottom, and maybe be too much flow for the betta. 




ben.


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## Nick potts (25 Nov 2020)

Are you seeing any issues due to the low flow? While good flow is important in high light, co2 injected setups, depending on your setup slow flow might not be an issue.

Also as you have a betta in there, you are going to have to sacrifice flow anyway, betta's prefer ( and in some cases need) very little water movement.

Nick


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## BanditCoaxx (25 Nov 2020)

Some of my plants on the right side aren't growing very well and it's having a bit of a diatom bloom, which I'm putting down to low flow. I do have a nano cube the betta can go in if I can't seem to rectify the issue but am hoping the spray bar thing could at least circulate the tank, just enough to not effect the betta too much, but to hopefully disperse the diatoms and spread nutrients around the tank.

ben.


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## dw1305 (25 Nov 2020)

Hi all, 


BanditCoaxx said:


> ....... and spread nutrients around the tank.


You don't need to worry about circulation in terms of mineral nutrient availability, the ions spread pretty equally through the water. You only need a minimal amount of circulation. 

It is a bit like adding salt to soup, once the salt has dissolved and you've given the soup a swirl, the soup is all salty, it isn't salty in some patches, but not in others.

cheers Darrel


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## Wookii (25 Nov 2020)

dw1305 said:


> Hi all,
> 
> You don't need to worry about circulation in terms of mineral nutrient availability, the ions spread pretty equally through the water. You only need a minimal amount of circulation.
> 
> ...



Sorry to piggyback on this thread, but can I ask Darrel, why doesn't it work like this with CO2 and DO - do dissolved gasses not disseminate through the water column in the same way as salts?


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## Nick potts (25 Nov 2020)

I am very likely wrong, but once dissolved i would think they would act the same.

As gas bubbles need a lot longer to dissolve into the water, the high flow helps keep them in suspension longer?

Darrel can tell me how completely wrong i am 😄


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## dcurzon (25 Nov 2020)

BanditCoaxx said:


> Some of my plants on the right side aren't growing very well and it's having a bit of a diatom bloom, which I'm putting down to low flow. I do have a nano cube the betta can go in if I can't seem to rectify the issue but am hoping the spray bar thing could at least circulate the tank, just enough to not effect the betta too much, but to hopefully disperse the diatoms and spread nutrients around the tank.
> 
> ben.


Could you just move your filter up to the top, so the flow goes along the top, down the glass and back along the bottom back towards the filter (aided by the draw of the filter) ?


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## Wookii (25 Nov 2020)

Nick potts said:


> I am very likely wrong, but once dissolved i would think they would act the same.
> 
> As gas bubbles need a lot longer to dissolve into the water, the high flow helps keep them in suspension longer?
> 
> Darrel can tell me how completely wrong i am 😄



Yes, but I mean specifically the dissolved gas levels - I use a CO2 reactor so I have very few bubbles in the actual water column, but with two drop checkers in tank, I can determine areas that produce a markedly lower colour response on one than the other even with somewhat strong circulation.


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## Nick potts (25 Nov 2020)

Wookii said:


> Yes, but I mean specifically the dissolved gas levels - I use a CO2 reactor so I have very few bubbles in the actual water column, but with two drop checkers in tank, I can determine areas that produce a markedly lower colour response on one than the other even with somewhat strong circulation.



Ah ok, no experience with reactors.

That is interesting, I would expect it to mix fairly evenly as Darrel stated for ferts.


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## dw1305 (25 Nov 2020)

Hi all,


Wookii said:


> why doesn't it work like this with CO2 and DO - do dissolved gasses not disseminate through the water column in the same way as salts?


They do, it <"just takes a long time">.

It is all down to <"solubility and the differential between the relative concentrations of the gas (at the gas exchange surface)">. Oxygen isn't very soluble, but it makes up 21% of the atmosphere. Pure water (H2O) (or any water with no BOD or COD) will reach equilibrium with atmospheric levels via diffusion eventually.


> The other, more significant, comparison with the oxygen diffusion coefficient calculated in air is the magnitude of the coefficient. The O2 diffusion coefficient in saturated air (15% oxygen) is 10,800 times greater than in water at 20°C)


This is also why we can  get <"supersaturation of oxygen"> under bright light, in eutrophic conditions, oxygen is being produced much more rapidly than its being lost. Turn the light off and we have the opposite effect, oxygen is taken up more quickly than it can be replenished and CO2 levels build up. We can <"use pH change"> as proxy for the O2 : CO2 ratio.








> Fig. 3. Surface pH values within the Mariager Fjord, Denmark, as reported in Hansen (2002). pH can reach very high values in coastal eutrophic waters during summer due to.
> the photosynthetic activity of algal blooms and near-constant sunlight, maximizing the influence of photosynthesis.


Carbon dioxide diffusion rates are similar to oxygen, but it is a much rarer gas in the atmosphere (~410 ppm) and <"much  more soluble">. If you aren't adding CO2 the situation is pretty similar to oxygen, but if you add ~30ppm CO2 it is going to out-gas pretty rapidly at the gas exchange surface, even when it is fully dissolved.

For CO2 I like the <"Bouncy Castle"> analogy

cheers Darrel


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