Ok, so just by chance I happened across a 75 gallon bowfront with a built in overflow, which I purchased instead of the 55 gallon I had from 8 years ago and had planned on using. My new question is regarding this overflow and how its supposed to work precisely. Its a corner overflow with 2 holes drilled in the bottom. First, I assume one is for the drain and one for the return, correct? If that's the case, then how does the "drain" bulkhead work? Does the water flow from the top of the overflow box all the way to the bottom and just fall through the bulkhead into a pipe underneath the tank to the sump, or should there be a PVC pipe inside the overflow box from the bottom to almost the top where the water will flow over, fill up the overflow box, then spill over into the PVC pipe inside the tank and flow down to the sump? Does that question make sense? I guess what I'm asking is how should the INSIDE of the built in corner overflow box look inside the tank?