Make sure there aren't any 'nippy' fish, as they will tear up his fins. Also, fish that are colorful and flashy (i've heard fancy guppies can be problematic this way) can be mistaken as bettas and attacked.
Good Luck! Jessupha lived in a 55, with a decent current for quite some time, and loved it. (until i put the background up- after a week of him constantly flaring at his reflection, i moved him.)
Warning: Although I read a lot, I'm new to this, thus take my suggestions with a grain of salt! ;)