Don't waste wild caught specimens.
The Black Rhom needs to have an aquarium of his own. They do NOT tolerate ANY tankmates.
The Gold Spilo can be shoaled with other Golds, but this is an adventure best suited to experienced P owners.
The Reds can be shoaled with any other P in the Pygocentrus genus. This includes Piraya, Caribe, and Ternetzi. You said it's a 55 gallon? That tank is FULL with 3 Red Bellies in it.
Mindy