I would empty the tank .. even for acrylics ..... Glass tank can crack (or bust a seam) with the water sloshing around. Acrylic tanks are meant to have their bottom completely supported when filled, lifting a full tank will bow out the bottom & crack it. <i3k ... it is not the weight of the tank that is the problem, it is the weight of the water on the bottom ... even half full, I would not move a big acrylic tank with water in.>