help! I've noticed that one of my guppy's opens his mouth and closes it constantly & really fast. He swims but after a while he just stays at the bottom of the tank. Also, he isn't that active any more. I'm thinking it has something to do with aeration? I have an airpump, filter and my tank's temperature is 82F. Water parameters were: Nitrite - 0, ammonia - 0ppm, Nitrate - 5.0, pH - 7.6++. I do 25% water changes every week. My balloon molly is doing the same, gasping at the surface then spits out bubbles. ? Any help would be appreciated. Thanks *SICK*