Above: One of the two rainbow cichlids I have owned. My avatar, of course.
Common name: Rainbow cichlid, Golden Red-eye cichlid
Scientific name: Herotilapia multispinosa, formerly Archocentrus multispinosus
Origin: Nicaragua, Honduras, and Costa Rica
Behavior: It depends on the individual, but in general they are a very peaceful fish, even while breeding.
Size: Usually 3-4 inches.
Minimum tank size: 20 gallon long
Tank setup: Prefers a sand substrate, and some caves for cover.
Tank region: Middle-bottom
Diet: They are an omnivore. They feed mainly on filamentous algae, simple algae, and diatoms in the wild. They also eat tiny fish and insects in the wild. They aren't fussy eaters in the aquarium, they'll take pellets and flakes, but like most fish you should vary their diet with live foods.
Breeding: They usually spawn on a smooth, flat rock, like slate. When they are ready to spawn they will usually start turning deep orange and black colored. They lay around 500-1500 eggs, which hatch after 2 days.
Compatibility: They will be fine with smaller fish, but will eat fry-sized fish. I wouldn't keep them with celestial pearl danios, or other fish of that size. Neon tetra size or larger is fine.
They will also do well with larger aggressive cichlids (in the right size tank), usually, but not in all cases.
Difficulty: Very easy to keep.
Water parameters: pH: Anywhere from 7.0-8.5 should be fine. Temperature: 68-82 Fahrenheit
Notes: They can live up to nine years. They can emit sounds from their swim bladders. Males have more pointed anal and dorsal fins.
They can be kept in large groups, but they do not need to be kept in them.