The Bolivian Ram (microgeophagus altispinosa), although territorial when breeding, is usually not agressive towards other fish. They prefer a temp of 75-79 deg F and a pH of about 7 although they will do fine at .5 in either direction as long as they are acclimated properly. They reach a size of 3-4 inches and average lifespan is about 4 yrs.
As for tankmates, most fish that have similiar water chemistry and temp requirements should be fine. Most of the Tetras, Hatchetfish, Corys, and about any other med size non agressive fish. I would stay away from the very small fish such as neons as they may become a meal. I think any of the Danios would be allright too. I would probably stay away from most of the barbs due to their fin nipping habits.
If you decide to try breeding them, be warned that the fry are EXTREMELY sensitive to nitrates and will die very quickly if there is more than a trace amount.
Logan J