Dam petsmart, they cannot make up their mind as to if the entire tank is tempered or not. They ar suppose to call be back and let me know. Anyways, I have two specimen boxes coming by mail incase I have to make an overflow box. In the rare case that the back glass is not tempered, where should I place the holes for the bulkheads? Also, how large should the holes be(I am looking for about 300 gph)? Lastly, ho much does it normally cost to get a tank drilled with two holes? :?: