Well i want to do bigger, but the stands footprint is 21" x 21" so as i'm sure you know, the only tank that is 20" long would be a standard 10G AGA tank. I mean.. maybe i could get away with something like a 15G cube, but i don't want to go through the trouble of looking for one, or even paying for one since i have a 10G on hand. Plus, all my plans for the sump have already been mapped out, and it's going to look real nice. I know 10G is small, but i only plan to have heaters and the return pump in the return section, since my tank is small enough to not need a skimmer. The return section will be about 7-8 inches of the tank, and the rest of the length of the tank will be dedicated to the refugium, which is the part i'm most excited about. Refugiums are freakin sweet. After a couple months of grow in with different types of algae and macro, they look amazing.