So last night while i was watching my Cory turned on its side and started floating. My tank is a 20 gallon and when I tested last night after he started floating I got 7.4ph ammonia nitrate and nitrite were all 0. My aquarium is freshwater and has been set up for a year and a half. I have an angelfish, a dwarf gourami, 3 neon tetra, 5 tiger barbs, and 3 Corys until last night. The tank temp is ~75 degrees Fahrenheit.