nice. I was just thinking about this subject today. Mine doesn't really count, because at the moment its only imaginary. in its infancy of the planning stage.
I have a 55 gallon, with a crack on one end. its at the top, sealed, and doesn't leak, but its kind of an eyesore. the stand its on will also fit a 75. I was thinking about getting a 75 and turning the 55 into a sump for it.
of course I know nothing really about building a sump. need to do some research in the DYI section. I do have a quick question about that, though. would it be better to run the HOB filters and the air bubbles in the main tank, or would they be just as effective in the sump? or would they be completely unnecessary, considering its a 55 gallon sump for a 75 gallon tank?
Edit: by the way, right now I'm running an emperor 400, a penguin 150, and some cheapo rated at 100 gallons per hour. hardly overfiltered. at least considering my bioload.