25 would be a little on the small side for convicts, but not horribly so, a 29 would do better for them. My personal experience has been that most if not all cichlids have very interesting personalities, the beatta suggestion was good as well, they have a lot of personality when you get them out of the 3 ounce bowls.
I am dying to own some rams, so if I had a 25, and nothing to put in it, I think I'd do a bunch of low tech plants and a pair of rams. JMO
dave