I just cleaned my tank yesterday and came home today to find my kole floating. Not sure what happened. He was eating fine and swimming around before I cleaned the tank. As I cleaned the tank he hid and that was the last I seen of him. All I did was use a gravel cleaner to empty 15% of my tank and scrubbed the rock with a softtoothbrush to get rid of some of the algae. Water parameters are fine. Any idea what may have happened or what I could do in the future so I don't lose another kole. I do have a Koran angel in the tank and he is doing fine....Thanks for the help.