They don't get too big 2-3inches and can be beautiful when they're full grown. But since he is a cichlid I would keep an eye on them. Bettas are slow and these guys can be quick when they want to be, though they prefer to be lazy too
. At the pet store I go to they like to keep a couple pairs in a 60 or more gallon tank and still have fights. I don't think they bother anything else much and there are a handful of angels in that tank too, but I would just watch them. Rams will do something simular to flaring they'll seem to charge and headbut each other but stop a half inch short and then "ram" again. Its cute but a territorial display and may freak a betta out a bit.