The shop I saw one at said that it would be cool in a 20 gallon. Is that too small. THe shop guy said that it did not get bigger then 7 inches, but I question how much he really knows.
Thanks for the help and for turning me off to the tank divider idea.

Twenty gallons is very small. You'd be a lot safer with a 50 gallon, which is what we recommend for the tank-bred bimacs that a lot of people are keeping.

You're right to suspect that the people at the LFS know very little and can't identify the species they sell. We've had plenty of reports of this happening.

Nancy