O2 levels with glass top

[gfink]

I used to have a biowheel and low light. Now I have a fluval 204 (with the return underwater) and a glass top. New light is coming in a day or so. With the glass top on and little surface agitation, will the fish get enough O2?

Here's some more info:
24 hours after moving my fish into the tank, I had two cardinal tetras die, and a third is starting to act weird. He is stwimming up at the top. All of the other fish are fine.

Ammonia 0, Nitrites 0, pH 6.8, temp 75°, GH and kH should be the same as the tank they came from. I think I am doing everything correctly...maybe it has just been too much stress moving them a few times in the past couple of days. What I find odd is that they are dying hours after I moved them, not just right away.

 

[PsiPro]

usually a sign of asphyxicatoin in fish is them swiming near areas of high flow water, but you do not have that. Did you leave both filters on at the same time for awhile so you dont have to re-cycle?

I would put your old filter or an airstone in if you think there is a possibly there is to little air.

In planted tanks, increasing light will increase O2 (to an extent), put any lights you have avaliably pointing at the tank to bring the tank up to 3wpg or so, that will add some O2 without the other filters or airstones.

Hopfully sombody who knows more can help you.

 

[gfink]

I have 3 peices of wood, some old eco-complete, and the old biowheel floating in the tank. That is a lot of surface area for bacteria. Ammonia 0, nitrite 0..it isn't a cycle thing. Well, hopefull no symptoms appear in other fish.

UPDATE: They definately aren't getting enough O2. All my other fish started to swim up to the top. I had my wife stir it around while I went out and got an air pump and stone. Now they seem ok. However, long term, I dont' want an air stone because I will be injecting CO2 (right?) My pump canister filter return is about 3" below the surface right now, and the surface ripples, but apparently that isn't enought air for the fish.

Where should the canister return be positioned?

 

[malkore]

I already replied to your other post, but keep running the airstone until you get the stronger light installed, and cO2 running.

If your plants aren't photosynthesizing quickly (i.e. you don't have high light and CO2) then they likely won't keep up with the oxygen demands of a full fishload.