I went out to my pond at daylight and didn't see any fish gasping for air so I guess that is a good sign. I have been using a sweetwater linear piston aerator with 1 round 9 in diffuser at 10 ft. I have been told that this was probably not big enough for my .3 acre pond, but I got one from a friend for free, so I figured it was better than nothing. It seems to be pushing a lot of bubbles in the middle and it is pushing 5 psi on the gauge. I am thinking of doing the horizontal aeration as well if my O2 levels are low. I will find out today what my O2 readings are. Maybe then I can find out if I lost a lot of fish.