Amongst the "old stalwarts", aquarium fishes that have been in the hobby for several decades, we can count a few of the South American cichlids. various Acaras like the Blue (Aequidens pulcher), Porthole (Cichlasoma portalegrense) the Keyhole (Cleithracara maronii), and Convicts (Archocentrus nigrofasciatus), are more mellow, easier bred and aquarium hardy having been through many successive generations of captive breeding.
Another "old timer" is the Firemouth, Thorichthys meeki, a real standard in our hobby that can be found in more fish stores than not. This is a relatively easygoing species that when raised and maintained in proper conditions can rival the beauty, interest and behavior of coral reef fishes.
Hobby literature citations abound with people keeping Firemouths in tiny systems of five, ten, fifteen gallons. Pairs should not be kept in anything smaller than twenty five gallons, a grouping of six in nothing smaller than a sixty. Smaller spaces will restrict growth, increase the likelihood of disease and result in much more injury and death from fighting.
Known as a or the "Beginner's Cichlid" for its wide tolerance to conditions, Firemouths are fine in most any source of tap/mains water. What does make a difference in their color and breeding behavior is temperature. These are tropicals that really appreciate warm water (see above). The low to mid eighties is fine for them every day, with a few degrees warmer for stimulating spawning.
For cichlids, Firemouths are rather shy and retiring. Unlike many other popular species of the same family, you will not find them out in front, jostling for space nor food generally. As such, if you're placing these cichlids with other cichlid species, it's strongly advised to introduce them in pecking order, the more easygoing first... and as always with aggressive fishes, observe closely for escalating agonistic behavior.
Most folks place Firemouths with other semi-peaceful cichlids, like Convicts, but I encourage you to consider a Central American biotope presentation instead, with fishes, plants and maybe even invertebrates found in the same setting. Many larger characins (tetras) and catfishes can be found from the same regions. Use the "Information by Country/Island" on fishbase.org to generate a list of freshwater fishes from Belize or Mexico.
As you might assume, after being in captivity for so many generations, this fish is very "plastic" about what it will accept in the way of foodstuffs, and it is. A staple diet of large flakes, pellets and sticks is fine, as long as it is augmented with occasional offerings of more meaty fare. Earthworms, bloodworms and shrimp are especially relished.
Unless your gravel is very coarse, you will find your Firemouths "mouthing" the substrate in the manner of Eartheaters (Juruparoids) for extra tid-bits. In the wild this species extracts insect and vegetable foods from the soft substrate in this way. A note re the use of auxiliary filtration here. Having good circulation and a particulate filter (e.g. outside power or cartridge) will co-benefit you in maintenance as well as your cichlids.
Sexing Firemouths can be a challenge... unless they're engaged in breeding activity, females can look a good deal like makes. The usual reliance on longer, more-pointed unpaired fins (dorsal, caudal, anal) of males is NOT a reliable indicator of sex, nor are the red, blue and green markings. Careful observation of a group will reveal the most dominant female/s, by its plumpness and slightly less elaborate finnage and males by their "blowing up" displays.
Conditioning of spawners, particularly females, cannot be overstated in importance. Egg-production and display of the female's genital pore are dependent of the supply of high quality foods (and water quality). If you're interested in spawning this species, pay attention to the kinds and frequency of high protein foods supplied.
Pairs spawn inside a cave of some sort, generally a supplied flower pot or pipe, typically in or towards evening. Depending on the size of the female, a few hundred eggs may be laid. Almost always the female will care for the eggs, males guarding the surrounding territory. Young hatch out in about three days time, with the female aiding in their release (with her mouth), spitting the young "wigglers" into a pre-dug depression. A day or two passes until they are free-swimming.
Newly hatched out young will live for about a day on their yolk sacs, then can be fed finely ground flake foods or newly-hatched brine shrimp. Additionally, you will likely see the parents supplying some of their food after being chewed up. At two to three weeks the young should be separated from the parents for grow-out.
Most often encountered are the parasites ich and velvet (Ichthyophthirius and Oodinium). Caught and treated promptly with standard chemical cures, outbreaks of these are easily controlled.
Balfar, Udo. 1975. Breeding cichlids "old friends". The firemouth cichlid (Cichlasoma meeki). Aquarium Digest Intl. 3:4, 75.
Konings, Ad. 1989. Cichlids of Central America. TFH Publications.
Loiselle, Paul V. 1985. The Cichlid Aquarium. Tetra Press, Melle Germany.
Montgomery, William H. 1984. Firemouths: the beginner's cichlid. FAMA 10/84.
Sands, David. 1986. A Fishkeeper's Guide to Central American Cichlids. Tetra Press, Blacksburg, VA.
Tavares, Iggy. 1996. Firemouth cichlids. FAMA 8/96.