It is small, but in my opinion if you can keep him alone in that tank it would be better than keeping him with your other fish causeing them distress. Are you planning to keep the rtbs solitary in 2 foot tank?
it has 3 9 week old platys in there at the mo, they are prolific breeders so i seperated the males from females, i could take them to my lfs though, what do you think?