It's an 8ft round tank, just about twice as deep. Which is good because I couldn't fill it to the brim anyway. The question is, how much give does one of these things have? My doors are only 6'9". If it had a little bend, it might work, but if it's rigid, I'd have to go for the smaller size (6'). I need to do some research on whether I can keep some of my current fish with a shark. Notably, the humu humu. The Tang would be OK, and the rabbitfish. The rest might get eaten. We shall see. I am considering using the 125 for a fuge. Any thoughts?