I recently purchased an Aqueon 45Gal tank and stand combo. The stand is on four feet that are a few inches in diameter. I was unable to shim under the feet to try and level the tank. So I drained it, got a piece of plywood and put the tank on the plywood. This sits on a carpet floor. The tank/stand now has a little motion forward and back if I put a little pressure on. I haven't noticed it moving on its own, but I can definitely move it without much force. How safe am I?