Best ways to add air to a large aquarium?

So I have a 180 gallon system, and admittedly it is a bit overstocked, but with 3 canister filters all rated up to 240 gallons each, I feel there is adequate filtration on the system. The water is always clear, and I do weekly testing and bi-weekly water changes. However, despite the presence of a 4-ft long buried bubble wand and an additional 1 ft bubble brick, and 2 powerful air pumps, I find the slower moving fish like my plecos and bichirs zooming to the surface to gulp 5-6x daily.

The tank also have two 1200 GPH circulation pumps on the bottom, 1 on either side, and two 600 GPH powerheads, 1 on either side.

Do you guys have any other methods for a sand substrate tank that can assist in increasing the air flow in the tank? Would like a permanent solution and doesn't have to be aesthetically pleasing, just needs to get the job done. Open to any suggestions, thanks!

spiff44 said:

Cool the water a bit maybe?

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There is a heat wave going on in California right now - been treating with ice cubes twice a day and a floating ice pack that only stays cold for a couple hours. The elevated water temperature in the tank is exaggerating the problem. Did a 25-30% water change again last night to cool the water down and remove nitrates.

brich999 said:

Many fish will go to the surface to grab air randomly. Does not mean that there isnt sufficient dissolved O2, some fish just do. Birchir and pleco do as do corys and many other fish. Birchir actually have lungs unlike other fish. Ive never used an air pump other than transporting fish but if you have surface agitation then gas is constantly being exchanged and I doubt low o2 is an issue.

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The canister filters each have a tube system return so that water is flowing on the surface constantly, but there's a pane of glass in the middle that the air bubbles hit when hitting the surface - is that cutting down on the available oxygen?

Drstrangelove said:

My pleco used to do this. Plecos use air for bouyancy, so I think they are simply replenishing their supply.

There are a few odd cases where O2 levels could be low:

1) the surface of the water is actually not in contact with air, but is in contact with the cover or some type of non permeable film. This could severely reduce oxygen in the water
2) the temperature of the water is extremely high
3) excessive amounts of organisms (plants lacking a light source, fish, bacteria, etc.) are consuming oxygen faster than it's being added to the tank
4) water in the tank is extremely stagnant

Otherwise, I can't imagine how your tank's oxygen levels would be low given how much you circulate it.

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Thanks for this list. From this, I can't deduce that this is a problem of stagnant water, seems like flow is just fine. I have seen some types of air pumps that are in bare-bottom tanks with a foam cylinder wrapped around them and a vertical plastic tube coming out. Do you know how these work? Do they work with sand bottom tanks?

Vanica said:

Perfectly normal behaviour for bichirs and plecos. Mine do it all the time.

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Do you other fish gulp at the surface or no?



Really appreciate everyone's help and quick responses!