Thank you everyone for responding and being so kind Moonstruck and Homedog. I'm trying the best that I can to keep these guys healthy, yes the glow tetra fish and the platy and goldfish are all 3 years old. I will research the re-cycling of the tank and learn how to keep the water parameters under control. Thanks so much. When I used to clean the tank, and strip it down, the fish would be placed in a fish bowl, individually. Only for about 20 minutes, then they would be added back into the tank. Maybe not a brilliant idea, but I wanted to try to clean the tank and take the bad bacteria out, even though I didn't know that I was messing with the good bacteria.