Probably going to get lauged at because I know i'm doing something stupid. But... I can't seem to get it to sink and stay at the bottom. It just floats to the top. Is there something I have to do to make it stay at the bottom of the tank?
Did you put the bottom part on ? Usually mines floats for like 20 minutes when I take it out and don't use it for awhile but when I put it on it takes a squeeze to get air out.