I'm working on slowly buying all the equipment for a 180 gallon DT, and I'm going to build my own sump. I've got a 40B and a 55 gallon tank that I have no other use for, and had thought about using for a sump. In looking at dimensions though, I think I'd rather have a 75 gallon tank for my sump so space would never be an issue, and clearly more water = more stability. The plan is to have the sump on the other side of the wall, so space under a stand is no issue. My question is if at some point a sump can become too big and cause any sort of issues.