Hey if the 180 proves to be a problem size wise I would skip over the 220 and go up further. Dont the 180 and 220 have the same dimensions except the 220 is 24 inches high. They probably wont notice the difference in the size of those two tanks. Because they pretty much like to hang at the top right? If it were me I would go for a longer tank...then they can really put on some speed before hitting the top
