i supported a 300 at my buddies house like this... we built a very nice wooden stand but he needed the tank up asap... used 8"x8"x16" blocks 4 high then laid 2x12 planks added 1" pink board and filled it up.... worked very good for a temp set up.... would work for perm one as well.... you can attach plywood to the planks to hide the blacks and make a door on the front...