sump filtration

Hello. I was looking at a setup that includes a 4ft tank, halide lighting and sump filtration. I do not think the current owner has tested the sump or the powerheads. but it seems powerheads are cheap so I am not that worried.

But what are the things I need to look at in the sump itself? It is made of glass so I suppose, I need to check for leaks/cracks in the glass. any other ideas?

how does a sump system compare to canister in terms of performance/maintenance/reliability?

thank you very much

Hi,
You need to see (or at least think about) how the sump operates in action. The problem generally with sumps and planted tanks is that they drive off CO2, and they do this by splashing the water, which is a bit like shaking up a bottle of cola. They are often unsealed or open to atmosphere which then allows the CO2 to escape. This means that CO2 consumption will be very high and inefficient. You should think about how to minimize splashing within the sump, i.e. does the water path change levels such as stepping down? And you should consider ways of sealing the unit during operation such as with a cover to minimise exposure to atmosphere. You should also think about getting pumps that will give you a total output rating of at least 10X the volume of tank+sump per hour. It this looks like it will be too difficult then think about just using external filter(s).

Cheers,

Hi all,
Sumps (and wet and dry trickle filters in general) are excellent at gas exchange, as suggested, for both O2 and CO2.
One of the problems with high volume external filters is that, at night with a heavy bioload, rapid initial oxygen depletion in the filter may mean that the majority of the biological media is oxygen starved and ineffective.

If you don't add CO2 to your tank CO2 levels are likely to be higher in the planted tank with a sump, as CO2 (and O2) will dissolve into the water in the trickle filter until it equilibrates with atmospheric CO2 levels (about 0.03% and 21% of the atmosphere respectively). If you do add CO2, it will outgas in exactly the same manner, and as 20ppm CO2 level is over 40 times the natural atmospheric content (0.39 ml CO2 per litre of water at 10oC), you could get through a lot of extra CO2.

cheers Darrel

Erm i dont get the last post. My own thoughts ( not based on experiance) is that a sump would lead to greater release of co2 from water because of the turbulance?

Hi,
You are right if there is more CO2 in the water than the equilibrium value with the atmosphere it will be lost, but if the water is CO2 depleted it will gain CO2 from the atmosphere until levels reach equilibrium (and vice versa).

Trickle filters work by having a large film of water which can exchange gases (N2, CO2 and O2) with the atmosphere.

You can think about like the diffusion of a coloured dye (say red food dye) through a permeable membrane (cotton handkerchief) into a bowl of water. The dye will diffuse out through the handkerchief until the water is uniformly pink, rapidly at first, but more slowly until an equilibrium level of pinkness on both sides of the membrane is reached. The rate of colour change will depend upon the permeability of the membrane (either how big the holes are and/or how thick the membrane is) and the eventual pinkness on how large a volume of water the bowl holds. If the volume of the bowl is large the final level of pinkness will be very low, and if it is very large it may well be undetectable.

In this case CO2 in the tank water is your dye, and the thin film of water (in the trickle filter) the membrane and the air surrounding your trickle filter the bowl. Assuming your sump is open to the atmosphere the CO2 will rapidly disperse into the surrounding air (so basically an infinitely big bowl) and be lost, the differential in CO2 concentration will remain large and CO2 will be out gassed from the water until it equilibriates with the atmospheric level. If, as Clive suggests, the filter in enclosed, the "bowl" will be much smaller and the differential between the levels of CO2 in the water and the air in the bowl much smaller, meaning diffusion will be much slower and more CO2 will remain in the water.

The effect of turbulence is to increase the area of water in contact with the air, you can just think of it as it makes it a thinner film. It is only if the CO2 level in the air is in equilibrium with water that it doesn't make any difference whether the water is turbulent or still.

Hope that helps.

cheers Darrel

Ok so if yoyu are injecting co2 it will probably lost alot quicker when using a sump becuase the concentration is higher in the water than the atmosphere and the greater turbulance in the sump releases it faster. I am just wondering about this becuase I am thinking about a future setup and whether to use a sump or my existing external filters. Aquarium would be a room divider and so there would bean issue with hiding filter pipes.

If you minimise the turbulence within the sump filter (having the inlet from the tank enter under the water, make sure any dividers or outlets aren't too near the surface) then the only effect of using a sump filter compared to a tank with an external filter will be that you have the surface area of the sump allowing CO2 out as well as the surface area of the tank.

I think you could just counteract this by having your CO2 injection on the return pipe to the tank. That would mean that CO2 rich water would be returned to the tank from the filter which is what you want.

Hello Ed,

I have been trying to find information and designs on the internet and what you say is certainly plausible, makes sense. I am just looking at all options at the moment, even closed loop with external filters. I actually have 4 filters running on my current tank (it was 5) and a sump could be a way of reducing costs, then again maybe i will just use what i have...

Hi all

I think you could just counteract this by having your CO2 injection on the return pipe to the tank. That would mean that CO2 rich water would be returned to the tank from the filter which is what you want.

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good idea.

I actually have 4 filters running on my current tank (it was 5)

Click to expand...

Depends what you use your filter for? if its biofiltration, a sump trickle filter would offer almost infinite amounts of biofiltration, the limit to filtration in most canister filters isn't the volume of potential sites for biofiltration in the filter substrate, but the relatively rapid de-oxygenation of the water inside the filter, meaning that a large proportion of the filter volume is irrelevant, as the water is de-oxygenated before it arrives. Bigger canister filters often do offer more filtration mainly because they have a larger volume of water flowing through the filter material, and this contains a greater volume of oxygen. In these cases paradoxically changing from a filter material with a high surface area to a less "good" one can often increase biological filtration. This is much more of a problem for people who keep unplanted tanks and a big canister filter, especially those who keep very clean unplanted tanks, without substrate and big, "messy" fish with a high oxygen requirement (some Panaque keepers for example), although dependent upon other factors this may occur even in planted tanks at night. This is why a lot of reef keepers take advantage of 24 hour photosynthesis by using a sump refugium with reversed lighting regimes (dark in the tank, light in the refugium).

A sump, return pump and powerhead(s) will give you filtration and water movement. I used to have a large planted "tank" with a planted overtank trickle filter, (constructed from guttering) that gave both the "riparium look" and absolutely enormous filtration, we had it in the lab fitted with a DO & ammonia probe and logger and used to do all sorts of horrible things to it (with landfill leachate), but it was a remarkably robust system. I can't find the photos but it was the "DeBruyn planted filter" on a large scale.

cheers Darrel