I have 4 keyholes, 3 Clown Loaches and Bristle Nose Plecos. 3 of Keyholes are fine but one is all black and hiding in a piece of pottery in the tank. Is this normal for breeding. Or the fish really stressed out. Doesn't really associated with any of the other fish. Is there anything I can do to help. Tanks got a ton of plants and rocks, drift wood and hiding places. My heater on the tank almost made it a fish boil. I have another heater in there. Water temp is at 72F. Any ideas or thoughts thanks. Oh yeah my tank is a 29 gallon tank.