They'll start breeding at about 2.5-3" for the male and smaller for the female. They'll max out about 5" or so.
Mine breed regularly on a piece of slate at the base of driftwood. Regular tap water (moderately alkaline, slightly hard). They're in with some Gymnogeo. "blue neons" and some other Uruguayan fish. They can hold their own but aren't really aggressive.
I've yet to have mine successfully raise babies in this environment. They get to free swimming and they kind of lose interest. I think the next step is to give them their own tank and add a diveder with some other fish on the other side (to keep their parental instincts up...but not actually be a threat). I'm also planning to siphon out some babies and raise them artificially.
Matt