Taxonomy & naming
The false firemouth was described by Charles Tate Regan in 1905 as Cichlasoma robertsoni, from material from the Atlantic slope of Central America (the type locality lies in the Stann Creek area of Belize). The epithet honours a collector named Robertson. Like most Central American heroines it spent the twentieth century in Cichlasoma, was later moved to Amphilophus and then to Astatheros as those genera were defined, and was finally transferred to the new genus Cribroheros when Oldřich Říčan and colleagues (2016) restricted Astatheros to its single Pacific-slope type species (macracanthus) and erected Cribroheros for the Atlantic-slope substrate-sifters — alfari, altifrons, bussingi, diquis, longimanus, rhytisma, robertsoni and rostratus. Cribroheros belongs to the heroine cichlids (tribe Heroini); the genus name refers to the sieve-like substratum-sifting feeding for which the group is known. The aquarium trade still circulates the fish as 'Cichlasoma' or 'Amphilophus robertsoni'.
Morphology
Cribroheros robertsoni is a moderately deep-bodied, medium-large cichlid reaching about 7.5 in SL. Its base colour is a pale pearly grey to cream, finely dusted with iridescent blue-green to emerald spangles that give the fish its 'emerald cichlid' trade name; a row of dark blotches forms a broken midlateral line, with a dark spot at the caudal-base, and the lower head and throat can flush a warm rose-orange reminiscent of a firemouth — hence 'false firemouth'. Colour and barring strengthen markedly with mood and breeding condition. The mouth is sub-terminal, fitting its sand-sifting habit. Sexual dimorphism follows the heroine pattern: mature males grow larger and develop more produced, pointed dorsal and anal fin tips, while ripe females are deeper-bodied through the belly and often show more contrasting flank markings and throat colour when in breeding condition.
Habitat
The false firemouth ranges along the Atlantic slope of northern Central America, from the Coatzacoalcos drainage of southern Mexico through the Yucatán lowlands, Belize and Guatemala into Honduras. It inhabits the lower and middle reaches of rivers in slower-moving waters, along with lakes, lagoons and floodplain backwaters, and shows a clear preference for soft substrates of sand, mud and small stones where it can sift for food. The water across its range is warm and generally hard and alkaline, in keeping with the limestone geology of much of the region; FishBase cites roughly 79–86 °F. It is an adaptable lowland fish, tolerant of a range of conditions from clear karst streams to turbid lagoons, which is part of why it is one of the more widespread and frequently encountered Cribroheros.
Feeding
Cribroheros robertsoni is an omnivorous bottom feeder and substrate-sifter, FishBase placing it at a trophic level near 3.4. It feeds by taking mouthfuls of sand and soft sediment and sorting out the edible fraction — small invertebrates (insect larvae, crustaceans, worms), with organic detritus and some plant material — expelling the cleaned substrate through the mouth and gills in the winnowing manner that gives the genus its 'sieve' name. The sub-terminal mouth suits this bottom-oriented diet. In the lowland river and lagoon communities it occupies it functions as a generalist forager of the soft-sediment zone, a characteristic member of the sand-sifting cichlid guild of the Caribbean slope.
Mating
As a heroine cichlid, Cribroheros robertsoni is a monogamous, biparental species that pairs and defends a joint breeding territory. Pair formation follows the standard cichlid courtship — lateral display, fin-flaring, jaw contact and cooperative cleaning of a spawning surface — with the pair intensifying in colour (the firemouth-like throat flush most evident at this time) and becoming territorial as spawning nears. The species is moderately aggressive and less combative than many of its larger relatives outside breeding, but a bonded pair defends its patch firmly. Pairs select and clean a hard surface in advance of spawning.
Breeding
Cribroheros robertsoni is a biparental open substrate spawner. The female lays a clutch of adhesive eggs — on the order of several hundred — on a cleaned hard surface such as a flat stone or sheltered rock, and both parents share extended care: the female tends and fans the eggs while the male guards the territory, the roles converging as the brood develops; once free-swimming the fry are guarded as a school by both parents, who lead them over the soft bottom where they begin to sift small foods. Eggs hatch in a few days at warm temperatures and the young grow steadily under attentive parental guard. The species is a reliable captive breeder, following the standard biparental-substrate-spawner pattern, and is among the easier Cribroheros to reproduce in the aquarium.
In the aquarium
The false firemouth is a well-regarded aquarium fish among Central American cichlid keepers — hardy, attractively coloured in good condition, and less belligerent than many of its relatives — though it is still a medium-large, territorial cichlid rather than a community fish. A single adult or a pair needs a tank of at least about 65–90 US gal, with ample floor space for a bottom-oriented sifter. Water should be warm (79–86 °F) and hard and alkaline (pH about 7.2–8.2), reflecting its limestone-lowland origins; strong, well-maintained filtration and regular water changes keep it in condition.
The key furnishing is a deep bed of fine sand, which lets the fish express its natural sifting behaviour and spares its gills the abrasion that gravel can cause. Furnish with rock and driftwood structure forming broken sight-lines and a flat stone as a spawning site; hardy, anchored plants tolerate a moderate digger. As a moderately aggressive, territorial species it mixes reasonably with other robust Central American cichlids of similar size and temperament — it is one of the more peaceable choices in its size class — with breeding pairs given space or their tankmates managed at spawning time; small or very timid fish are best avoided. Feeding is easy: a quality sinking cichlid pellet staple plus frozen and live invertebrate foods (bloodworm, brine shrimp, prawn) and some vegetable matter, with the sand bottom encouraging natural sifting between feeds. The main husbandry notes are to provide sand rather than gravel and to give the fish hard, alkaline water; it is otherwise an undemanding and rewarding species.
Conservation
The IUCN Red List assesses Cribroheros robertsoni as Least Concern (assessed 2018), reflecting a wide distribution across the Atlantic-slope lowlands from southern Mexico to Honduras, abundant and adaptable populations, and a tolerance of a range of habitats. It is taken locally for food and for the ornamental trade, but neither is regarded as a population-level threat to so widespread a fish. The broader pressures on its lowland river and lagoon habitats — deforestation and agricultural runoff, water extraction, pollution and introduced species — are the familiar watch-points for the Mesoamerican freshwater fauna but do not presently threaten this successful, adaptable species. It carries no CITES listing.