yeah 20 long until they're half grown. but that takes years. if you have one convict chances are you might want more cichlids in a few years : )
cons like friendly company though, they're pretty much swarm animals when yonger, but they're happy in tanks as pairs.
I personally think its sad to see a male cleaning a rock or digging a pit all day, being a single male myslef. I'd get him a few girlfriends, let him choose one, and then give the others away. But of course they are convicts, so you'll have to plan ahead to have something to do with the thousands of babies they will start having right away. The best thing to do with them in my opinion is to find someone with a bigger non-cichlid fish that will eat them. I have a clown knife for this. Convicts are so prolific you'll never be able to find homes for all the babies they produce.