I had two dead catfish this morning. But no more during the day and they've stopped surfacing so maybe the aeration is helping some. Is this an indication the oxygen is coming back up?

I guess I'll check out the trash pumps tomorrow.

My pool pump is basically the same idea as the trash pump although probably not as powerful. Basically I stuck a 2" PVC pipe on the intake capped the end, drilled a bunch of holes in it and stuck it about 3' underwater. The outlet goes to another piece of 2" PVC, capped and drilled - this is aimed up in the air and directed back to the pond surface.