Hey all I'm new here, but unfortunately my first post is not a good one. I have a 10 gal. tank, and have been experiencing ammonia problems. I have been keeping them down with water changes, and the fish have been doing fine...until tonight. I did about a 50 percent change, and now my two angels are at the waters surface gasping for air. Before the change they were not doing this. I treat my water before it goes into the the tank with Tetra bio safe. I think the ammonia damaged their gills, but they weren't doing this before the change. Any help would be greatly appreciated.