for a 55, go with the congos as suggested, but instead of a bichir or a rainbow shark, get a school of 6 corydoras.
red tailed black sharks get to aggressive with congos for them to be in the same tank, and bichirs get to big for a 55 gallon. most get to be around a foot long and they get fat too.
red tailed black sharks get to aggressive with congos for them to be in the same tank, and bichirs get to big for a 55 gallon. most get to be around a foot long and they get fat too.