I wouldnt.. I had to get a 150 gallon tank. Mine got to 9" and 10". I am lucky that one is submissive but when they were younger, Raina bit Sylvie's tail clean off

. I wish I would have only gotten one ..would have saved me a lot of money (and floor space!). Its neat to watch them together..they love each other.. but I still always worry because Raina still flutters at her all the time. Plus, if you get a female that lays eggs..its really stressful. In my tank, Sylvie became dominant when she was laying eggs..I feel like I really dodged a bullet because Raina was nice enough to back down and let her. They switch back when she was done. I also got them at the same time when they were teeney tiny... I am not sure how it would go since yours isnt a baby anymore.