Taxonomy & naming
The Mexican ichthyologist Juan Jacobo Schmitter-Soto described Amatitlania coatepeque in 2007, in his revision of the genus Archocentrus (Zootaxa 1603) — the same paper that erected the genus Amatitlania for the convict and its allies. The type locality is the north shore of the island in Lake Coatepeque, and the fish was described as a Coatepeque endemic, split from populations long lumped under the true convict, Amatitlania nigrofasciata. The epithet simply names the lake. That standing has been disputed almost from the start. McMahan, Matamoros and colleagues (2014) re-synonymized Amatitlania coatepeque with Amatitlania nigrofasciata, arguing the diagnostic characters did not hold, and the hobby authority Juan Miguel Artigas Azas has likewise treated the convict as a single wide-ranging species. Molecular work finds the divergence among these forms shallow. Eschmeyer's Catalog of Fishes nonetheless lists coatepeque as valid — Amatitlania coatepeque Schmitter-Soto 2007 — noting it was considered a synonym by some workers before being treated again as distinct. This profile follows that catalogue treatment while flagging plainly that the validity is genuinely contested.
Morphology
Amatitlania coatepeque is a small convict-type cichlid reaching about 3.5 in in standard length (FishBase), with the compact oval body and dark vertical barring typical of the group on a pale grey to bluish ground. Schmitter-Soto's 2007 diagnosis separated it from the true convict on fine technical characters: details of squamation — including the interradial scale rows on the anal fin — the peritoneum, and osteology. Those are exactly the characters McMahan et al. (2014) found did not reliably distinguish the Coatepeque population, which is the crux of the synonymy dispute. To the eye it is a convict like any other, the same barred grey body and finnage, with no obvious badge to separate it at a glance from Amatitlania nigrofasciata. Sexual dimorphism follows the convict pattern: males run larger with longer, more pointed unpaired fins, while females are smaller and rounder, ripe females often developing an orange wash on the lower body.
Habitat
As described, the species is known only from Lake Coatepeque — a deep, clear volcanic crater lake of the western Salvadoran highlands, set in the caldera of the Coatepeque volcanic complex. Crater-lake endemism is a recurring theme among Central American cichlids: isolated volcanic lakes have repeatedly produced locally distinct forms, the Nicaraguan crater lakes being the classic example, and that pattern is part of why a Coatepeque convict was proposed at all. The lake is warm, clear and mildly alkaline, with rocky and sandy shores. FishBase publishes no species-specific temperature or pH range, but the setting implies the warm, hard, alkaline water typical of the convict's range. If the synonymy with Amatitlania nigrofasciata is accepted, then 'coatepeque' is simply the Coatepeque population of a wide-ranging species rather than a true single-lake endemic — a distinction that changes how its range is understood.
Feeding
Amatitlania coatepeque feeds as an opportunistic omnivore in the manner of the convict group, taking aquatic insect larvae and other small invertebrates, algae, fine plant matter and detritus gleaned from the lake's rocky and sandy bottom. No dietary study specific to the Coatepeque population has been published, so the picture is the genus-typical one — an adaptable generalist rather than a specialist. In a clear crater lake it would work the structured shoreline as a benthic gleaner, much as the true convict does across its broad range.
Mating
Like the rest of the convict group, Amatitlania coatepeque is a monogamous, biparental, pair-bonding cave-spawner. A male and female pair off and together choose and defend a cavity among the rocks, working through the familiar cichlid courtship of lateral display, fin-spreading and shared cleaning of the spawning surface, the female's deepening colour signalling her readiness. No behavioural study specific to the Coatepeque population exists, so this is the genus-typical account — but the convict's pair-bonding, cave-spawning biology is among the best-documented in all of Central American cichlids, which makes the inference a secure one even for an unstudied population.
Breeding
Amatitlania coatepeque is a biparental cave-spawner, laying adhesive eggs on the wall or roof of a chosen cavity. The female fans and tends the clutch while the male defends the territory, and both parents then lead and guard the free-swimming fry as a school. The true convict to which it is so closely tied is one of the most prolific and reliable of all aquarium cichlids, regularly raising large broods, and the Coatepeque form would be expected to breed the same way. No clutch-size or spawning data specific to coatepeque are published, so no separate figure is asserted here — its breeding biology is taken to be that of the convict complex rather than something documented for this contested population.
In the aquarium
Amatitlania coatepeque is more a taxonomic and locality entity than a distinct aquarium fish: convicts of Coatepeque provenance are not separately established in the trade, and any keeper would treat one exactly as a true convict — a hardy, prolific, strongly territorial small cichlid that breeds with almost no encouragement.
Tank: around 25 US gal or more for a pair, with a substrate of sand and gravel and an aquascape of rocks and bogwood arranged into caves and broken sight-lines, including dedicated spawning caves.
Water: warm, around 75–82 °F, moderately hard and near-neutral to alkaline (pH roughly 7.0–8.0), with good filtration and regular water changes.
Feeding: trivial — an omnivore that takes flake, pellets and frozen or live foods readily.
Common mistakes: underestimating the convict's signature aggression around fry, which makes a breeding pair a poor community citizen. If the synonymy stands, keeping 'Amatitlania coatepeque' is simply keeping a convict from a particular Salvadoran lake, and the husbandry is identical — that is the honest framing.
Conservation
Amatitlania coatepeque has no separate IUCN Red List assessment under that name; FishBase records its status as Not Evaluated. That gap is itself a consequence of the taxonomic dispute: because the field has not agreed the Coatepeque population is a distinct species, it has not been assessed as one, and it is folded into the unsettled picture of the convict complex — the true convict, Amatitlania nigrofasciata, was rated Data Deficient precisely because the Amatitlania siquia / Amatitlania coatepeque taxonomy remains unresolved. If coatepeque is a valid single-lake endemic, it would warrant attention as a narrow-range species exposed to the pressures on Lake Coatepeque: pollution and nutrient loading, shoreline development and tourism, and introduced fishes. If it is merely the Coatepeque population of a wide-ranging, abundant convict, the concern largely dissolves. No assessment under the name exists to settle which framing applies, and no IUCN category is invented for it here.