Actually, I'm keeping a pair right now.
I love these fish, they're really laid back for cichlids, and a pair can live with a large selection of tankmates.
The male top out at 10" by the end of its fairly extensive life, the females will grow up to 6". I've got them in 110 gallon now, with a dozen congo tetra's, a royal pleco, and a bunch of synodontis catifsh. The size of tank i've donated to them is overkill, but a standard 55 is about as small as i'd go for a pair.
They're hardy fish, all they ask for is clean water. Unless you want to breed them, ph isn't much of a concern. It's good to have a couple of places where the female can get away from the male - he can get moody at times. They're cave spawners. I just used a mix of rocks, wood, and ornamants to create a variety of hidey-holes for them to choose from.
If you were planning to add it to a cichlid tank, stick to calmer species like severums or eartheaters - these guys won't stand a chance against any of the meanies. They're really at their best as a pair that rule the nest, IMO.