If it's just the tank and not the stand that moves, the stand was built with a crooked beam of wood supporting the tank. The tank weighs over 400lbs when full so, it shouldn't move at all. If you get the chance, you could put a thin sheet of styrofoam or carpet padding between the tank and stand. This way the tank will find its' own level position and you'll reduce any uneven stress points that can lead to the tank cracking or busting a seal.