so ive been exploring ways to cut the cost and getting a large fish tank. and today i ran across someone selling a "vision reptile cage" that comes to be about 630 gallons. however im unsure as to wether i can make this withstand the pressure and or leak proof. has anybody ever done this before? manufacturer says its a "molded one piece construction from durable high density impact resistant polyethylene. " but no thickness is given. the dimensions are 7 feet wide, 3 feet deep, 4 feet high. any ideas or advice?