Taxonomy & naming
Jay R. Stauffer Jr. and Kenneth R. McKaye described Amphilophus xiloaensis in 2002, in the same paper — "Descriptions of three new species of cichlid fishes (Teleostei: Cichlidae) from Lake Xiloá, Nicaragua," Cuadernos de Investigación de la UCA 12: 1–18 — that also named its lake-mates Amphilophus amarillo and Amphilophus sagittae. The type locality is Lake Xiloá (Laguna Xiloá) itself, and the epithet simply records that home: a place-name, not a person.
The fish sits in the cichlasomatine genus Amphilophus, within the Midas cichlid species complex centered on Amphilophus citrinellus — the same lineage behind the aquarium trade's "red devil" and "Midas" cichlids. Telling it apart from its relatives is genuinely hard. By Stauffer and McKaye's own key it differs from Amphilophus citrinellus mainly in a smaller eye, and separating it from the sympatric Amphilophus amarillo can come down to internal features such as gill-raker counts rather than anything you could see in a photograph. That subtlety is the point: these are young, barely-separated species, and the literature still hedges on exactly how many distinct forms Lake Xiloá holds. In Nicaragua the fish is called simply mojarra, a catch-all Spanish name shared across the country's cichlids rather than a trade label of its own.
Morphology
This is a deep-bodied, stocky, full-sized Midas cichlid. The original description and FishBase give a maximum of only about 6.5 in standard length, but that figure comes from a handful of wild type specimens and badly understates the fish. Like the rest of Lake Xiloá's benthic Midas forms, Amphilophus xiloaensis reaches roughly 12 in total length in aquaria, with large males approaching 14 in; keepers routinely report 8 in males. For comparison, the Greater Chicago Cichlid Association puts males of the sister species Amphilophus amarillo near 14 in and recommends a six-foot tank for Amphilophus sagittae. This is a big cichlid that needs the room of one, not the medium fish the standard-length figure implies.
Colour is both its most striking feature and its biggest identification trap. Most wild fish wear a barred grey "normal" pattern, but Lake Xiloá's Midas cichlids span the full range — white, yellow, orange, even red individuals, plus blotched "marble" intermediates. These gold and amelanistic morphs are natural, not breeders' creations, though they occur at low frequency: gold fish make up less than about a fifth of Amphilophus xiloaensis. The sexes look essentially identical; breeding females may briefly develop a modest nuchal (forehead) bump, and males simply tend to run a little larger. Because colour and shape overlap so heavily with Amphilophus citrinellus and Amphilophus amarillo, reliable identification rests on locality and fine morphometrics rather than any single field mark.
Habitat
Amphilophus xiloaensis lives only in Lake Xiloá, a roughly 2 mi² volcanic crater lake on the Chiltepe Peninsula about 12 mi (12 mi) north of Managua, set against the western edge of Lake Managua (Xolotlán). The IUCN treats it as a single-location endemic with an extent of occurrence and area of occupancy of only about 5 mi² — essentially the lake itself. The crater is geologically young, on the order of 6,000–6,500 years old, and once drained to Lake Managua, which seeded it with a Central American cichlid fauna. For so small a basin it is varied: a steep, rocky basalt shore in the north below the Apoyeque volcano grades to flat sandy beaches in the south. Volcanic heating keeps the water warm and stable at around 84 °F (84 °F), sulfurous gas bubbles up through the bottom in places, and the chemistry is hard and alkaline, roughly pH 7.5–8.0.
Within that mosaic Amphilophus xiloaensis is a rock-associated fish (Stauffer & McKaye, 2002) and the lake's deeper-living, bottom-oriented Midas ecomorph. FishBase gives an occurrence depth of about 6.5–26 ft (7–26 ft), though in-situ accounts follow it well down the basalt slope, so its range is better read as "shallow rocky shore into the deeper benthos" than as a fixed figure. It shares the water with other Managua-basin cichlids, among them Parachromis dovii, Parachromis managuensis, Hypsophrys nicaraguensis and Neetroplus nematopus — a reminder that Lake Xiloá is a small annex of the great-lake fauna that grew its own endemics.
Feeding
Like the rest of the Midas complex, Amphilophus xiloaensis is a benthic generalist with a durophagous streak — FishBase places it at a trophic level of about 3.3, an omnivore leaning carnivorous. Its signature tool is the modified lower pharyngeal jaw, a millstone-like plate of molariform teeth that lets Midas cichlids crush snail shells. Direct stomach-content studies for this species are thin, but its jaw closely tracks that of the snail-specialist Amphilophus amarillo. The telling difference is that Amphilophus xiloaensis carries a few more rakers on its first gill arch, a finer sieve that lets it take smaller items — so it is a shade less of a hard-shell specialist and a shade more of a generalist. That kind of small trophic shift, repeated across the complex, underlies Lake Xiloá's parallel "limnetic," "shallow-benthic" and "deep-benthic" ecomorphs. In the community it feeds at mid-level — neither apex predator (that role falls to Parachromis) nor strict herbivore — and, like all Amphilophus, it gains weight easily, so a measured diet matters more than a varied one.
Mating
Outside the breeding season, Lake Xiloá's Midas cichlids are largely non-territorial, moving through the lake in loose, mixed-age groups and leading a more or less nomadic life. That changes the moment pairs form: the fish becomes intensely site-attached, defending a patch of the basalt boulder field against all comers, and because nesting is colonial the breeding grounds grow crowded at peak season. The most interesting wrinkle is mate choice. Work by Elmer and colleagues found that these fish mate assortatively by colour, preferring partners of their own morph. Since a fish cannot see its own coloration, that preference points to a heritable, behaviourally reinforced divergence — sexual selection helping pry incipient species apart even as they spawn side by side, evolution caught in the act. For the keeper, that same flip from sociable to fiercely territorial is the practical hazard: tolerance drops sharply once a pair comes into condition, and fish this size can injure each other and their tankmates at close quarters.
Breeding
Amphilophus xiloaensis is a biparental substrate spawner — both parents guard the eggs and fry rather than carrying them — and it breeds colonially among the basalt boulders. Timing varies a little between sources: the IUCN assessment, drawing on Elmer et al. 2009 and Recknagel et al. 2013, gives a December–February peak, while at least one diver's account puts the height in November–December. Either way it is a short, synchronized seasonal pulse shared with the lake's other Midas species, and it plays out primarily over rocky habitat. Clutches are large — on the order of 1,000 eggs — glued to a cleaned rock surface; they hatch after about three days, and the fry are free-swimming roughly a week later. Both parents tend the brood through that free-swimming stage, the prolonged biparental care typical of the Midas complex. The species is a specialist's fish rather than a common import: it first reached European hobbyists around 2001, before it even had a name, and it remains uncommon in the trade.
In the aquarium
Difficulty is intermediate-to-advanced: the water chemistry is undemanding, but the tank size, the breeding aggression, and the need for verified stock put this fish beyond casual fishkeeping. It is rarely seen outside dedicated Central American cichlid collections — imports are sporadic, most specimens in circulation lack verifiable locality data, and no trade name flags it reliably on a shop label, so keepers usually source it through specialist breeders or hobbyist networks.
Tank: allow at least 10 ft (about 10 ft, or roughly 300 US gal) of length, more for a pair — the guidance from the AquaInfo / NVC keepers who first kept it in Europe. That is not excessive for a fish from a 2 mi² lake; it reflects how badly a large Midas cichlid can injure a tankmate, or its own partner, in tight quarters. Give it a diggable sandy or fine-gravel bottom, heavy basalt or smooth river-rock for shelter, and filtration sized for a large, heavily-fed cichlid.
Water: warm (81–84 °F / 81–84 °F), stable, hard and slightly alkaline (pH 7.5–8.0), with a moderate dose of aquarium salt to match the crater's volcanic minerals; soft or acidic water is inappropriate, and the temperature should not fall below 81 °F (81 °F).
Feeding: it readily takes quality pellets, frozen foods and invertebrates, but the lineage tends toward obesity, so keep meals measured rather than ad libitum.
Tankmates: outside breeding it is only moderately aggressive and can share a large, well-structured tank with other big Central Americans, including its natural lake-mates Hypsophrys nicaraguensis, Parachromis managuensis and Neetroplus nematopus; once a pair bonds, tolerance collapses and both partners defend hard, so a breeding pair is best given its own tank or a very large one with escape routes.
The overriding rule: never house Amphilophus xiloaensis with other Midas-complex fish (Amphilophus citrinellus, Amphilophus amarillo, Amphilophus labiatus and their kin). They hybridize freely, the young are indistinguishable by eye from pure stock, and a cross destroys the intact-endemic value that is the only reason to keep it — the same reason a photo alone cannot confirm identity, since much of what circulates as "xiloaensis" is unverifiable without locality data.
Conservation
The IUCN Red List assesses Amphilophus xiloaensis as Vulnerable under criterion D2 (Lyons & Contreras MacBeath; assessed 22 July 2019, published 2020). The listing rests on geography, not observed decline: the fish is known from a single location with an area of occupancy of only about 5 mi², its population trend is judged stable, and it is recorded as "not utilized," with no fishery or aquarium-trade harvest. D2 is essentially a precaution — a species confined to one tiny lake sits one bad event from trouble even when nothing is currently wrong. Here that event has a name. Lake Xiloá lies inside the Chiltepe Peninsula Nature Reserve and, unlike much of Nicaragua's waters, has so far escaped colonization by introduced tilapia (Oreochromis spp.), whose spread McCrary et al. (2007) tracked across the country; an establishment of tilapia, or a shift in land use around the lake, is the single largest plausible threat to a single-lake endemic. This is not the heavily polluted Lake Managua (Xolotlán) just downslope — Xiloá is a separate, far cleaner crater lake, so the danger here is confinement and invasion rather than present-day pollution. The regional backdrop sharpens the stakes: several other Nicaraguan crater-lake Midas cichlids are already listed as Critically Endangered (McCrary, 2024), which makes the cautious Vulnerable rating a snapshot of a currently secure but inherently fragile fish.