Canister filter water return...how far below surface....

[gfink]

How far below should I keep it so CO2 doesn't outgas, but I get enough O2? Right now, I have it setup about 3 inches below the surface...the water is moving on the top, but the fish started to run out of O2 after about a day. Right now I have a bubble stone in there until I find the right height.

New lights come on Monday and that should help the plants to make O2, and I will be doing DIY CO2 soon after.

Prior to this, the tank had a biowheel, so it had plenty of O2 in it.

Thanks for helping.

 

[IceH2O]

From the waterline to the middle of the spraybar its 1.25 inches on my tank. From top of tank to spraybar is 3 inches. I have my spraybar pointed slightly down about 10-15 degrees. But I also have a HOB since I don't inject, so I don't know if this will help or not.

Why not just lower the water level till you find a comfortable area for the fish? It'll be easier than moving the spraybar up and down.

 

[malkore]

Disturbing the water's surface is what creates gas exchange: CO2 leaves, O2 enters.
at 3" down, if its perfectly level, it shouldn't agitate the surface at all, so next to no gas exchange occurs.