Thanks everyone for the information! It's really helpful. I would like to keep him in the 20 as long as possible, but im sure I could find a way to fit another 40 gallon if needed, or I will try to find a 30 gallon. Does gender play a role in the average length (like BPs)? And pics of setups would be cool if you want to share them (don't have to if you don't want to).