Hypoxia isn't the only thing that will cause fish to pipe on the surface. Unionized ammonia and nitrites will also do it. Been there done that with a small pond that had too many fish in it, and it paralleled higher water temps due to the fact that unionized ammonia levels go up with higher temps. They were yellow perch and bluegills in a holding pond.
Trout are much more sensitive to unionized ammonia and nitrites than other species.
Ammonia and nitrites can be easily tested for with an aquarium test kit. You can determine unionized ammonia by matching total ammonia to ph and temperature. With trout any unionized ammonia levels above 0.020 ppm are detrimental.
Last edited by Cecil Baird1; 03/19/13 07:51 PM.
