AFAIK occies wont form a colony as easily as multis and are more of a harem breeder. I don't think a 29g would have nearly enough space for more than a couple male territories so make sure you are certain about which sex you are getting if you go with that many initially.
The calvus will eventually outgrow the 29g, although they are apparently a slow growing species. That being said, I wouldn't do 5 and would stick to more a pair or trio (1m/2f) or something along those lines. Also keep in mind they have fairly large mouths. I'm not sure at what point, if any, an adult size occie would be in trouble...but fry/juvies might not last long. Just my thoughts though...