Does anyone know if either Petsmart or Petco will do tank trade in's? I noticed that one of my local Petsmarts had a collection of old used tanks for sell. Do they just take donations, or will they credit you? I have a tank that I've done some work on, but I'm picky and there's some scratches on it that I just can't stand, so I was wondering if I could take the tank in and pay the difference for a new tank.