I have a 125 gallon tank I use as a sump for my 362+- gallon tank. As for drilling don't be afraid. It's easy, just go slow and steady and make sure the glass hasn't been tempered. I generally start my drill on a slight angle which keeps it from walking around on me. There are plenty of videos on the net of how to do it and it really is as simple as they make it seem. Congrats on the purchase!