Sitting here I keep hearing a clanging noise, but each time I go and check on Tigger (oscar) he is just hovering in the water minding his own business. Soon as I move, clang again. So I have stood on the stool and spied on him over the top of the pc and noticed he is doing the clanging, gone to the tank again and just noticed the heater is no longer attatched to the suckers