Fish freak out and gasp when light is turned off HELP
Hello guys first time post here,
Recently got a 10 gallon tank with a hang on back filter, heater, thermometer, and an air pump. I have 4 Pretty Tetras and recently 2 Corydoras. When i turn off the light the Prettys all swim rapidly at the surface of the water and gasping. The Corys on the other hand have not acted this way since i've got them. I thought it was due to ammonia/ low oxygen but i test everytime and it does not come up to even low levels of ammonia and I have the air pump for oxygen now. I have also tried turning on my room light and keeping it on for a period of time after I turn my LEDs off but still they do this.