Just something I am thinking about. I can't because of space issues have a fish room so if I were to get a larger tank it will have to set in the same place my 125g is at. I am looking to get either a 5 or 6 foot long tank either 30 or 36 inches wide. I was thinking about using my 125g tank as my sump. It has one hole drilled in the bottom left corner inside my over flow box that would have to be plugged. Here is the real question, lol. Because of space issues I really don't have room for a frag tank that I would like to have, that space is taken by a quarantine tank that I want to keep. Soooo what I was thinkin was, plug the hole in the 125g, put a divider in the 125g tank and use one side for the sump and make the other side of the 125g a frag tank. I would put a MH light over the frag tank and run that light at night when the lights in the DT are off. The section of the 125g that would be a frag tank would only be 2 foot long. I could drain the over flow from the new DT down into the frag tank and then ( haven't thought this out yet) have an overflow from the frag tank into the sump part of the set up run the water thru the skimmer and then pump it bck into the DT. I could just use two tanks, one for the sump and the frag tank under my stand, I just thought this might be an eisier plumbing job if they were both in my 125g tank. Like I said, this idea is just a thought. I wish I had been in this hobby before we built the new house and I could have built a fish room at that time, lol.