Quote Originally Posted by mr. s View Post
I had a heater that I thought was broken. I plugged it in and it never warmed up. Turns out that it just lost heat quickly. I put it under the tank and put a layer of cardboard and then styrofoam to make sure that the heat was not being lost to the dresser it is on. I waited several hours before I checked the temperature age and it has not given me problems since.
Most say to have air under them so they dont over heat or something like that. Thats why they come with the rubber feet to lift up aquariums.