1.5" bulk head with a threaded male end through a 1.5" hole would work just fine. Use the male threaded side through the bottom of the drilled hole with an "O" ring between the fitting and the glass, get a same size female threaded on the top side, same thing, use an "O" ring between the female fitting and the glass. Youll definatly need ot get an over flow kit like Bumblebee mentioned, the sell all types and configurations, so that will depend on what type of over flow your wanting, whther it be in the middle or on the corner. Youll dirll your hole for the bulk head behind the overflow on the bottom of the tank, plumb it down into the sump, return it back to top of tank.