Taxonomy & naming
The Angostura cichlid was described by Uwe Werner and Rainer Stawikowski in 1987 as Paratheraps breidohri, in the German aquarium magazine Die Aquarien- und Terrarienzeitschrift (DATZ), from material collected in Chiapas, Mexico (holotype ZFMK 15524). The epithet honours Hans-Günther Breidohr (1938–2015), a German cichlid aquarist from Wuppertal who collected with the describers. As with the rest of the Middle American assemblage the species was subsequently moved through Cichlasoma and Paraneetroplus before settling in Vieja, where the Catalog of Fishes lists it as valid (Vieja breidohri). It sits in the Neotropical subfamily Cichlinae among the heroine cichlids, and the modern herichthyin revision (McMahan et al. 2015) and later checklists retain it in Vieja. Being described comparatively recently and from a restricted system, it is one of the better-circumscribed species of the genus, though much of its natural history remains thinly documented.
Morphology
Vieja breidohri is the smallest species in the genus: FishBase gives a maximum of about 6.5 in, well short of the 10–14 in of its larger relatives. It is nonetheless built on the familiar Vieja plan — a deep, laterally compressed body with a steep forehead, the largest males developing a modest nuchal hump. Conditioned adults can be handsomely coloured, the olive-grey ground tone giving way to pearly blue-green flanks with a series of dark mid-body bars or blotches and, often, a dark spot at the base of the tail; the head and breast may flush warmer tones in spawning fish. Subadults are plainer and more uniformly silvery, the markings and colour sharpening with maturity. Sexual dimorphism follows the genus pattern: males grow somewhat larger and carry the heavier forehead and incipient hump, ripe females are deeper-bodied; the sexes are not easily separated outside breeding condition.
Habitat
The Angostura cichlid is a narrow-range endemic of the Grijalva River system on the Atlantic (Caribbean) slope of Chiapas, southern Mexico, with the Catalog of Fishes giving its distribution as the Río Grijalva and the Presa de la Angostura — the large hydroelectric reservoir that gives the fish its common name — extending into the borderlands of northern Guatemala. It is a fish of warm, slow, low-gradient water: the calm reaches of rivers, lagoons and, prominently, the still water of the Angostura impoundment, over soft mud and sand among submerged wood and structure. In-situ and aquarium-derived chemistry point to warm, near-neutral to alkaline, moderately hard conditions, consistent with the lowland and reservoir habitats of the middle Grijalva; like the rest of the genus it favours quiet water rather than strong current.
Feeding
Vieja breidohri is a smaller-bodied omnivore with the herbivorous and detritivorous bias typical of its genus. It works the soft bottom and submerged structure of slow water for plant material, algae, detritus and the small invertebrates living among them, using jaws suited to grazing and tearing vegetation rather than pursuing prey. In the riverine and reservoir community it functions as a grazer and processor of plant detritus, taking animal food opportunistically as all cichlids do. Its compact size means it forages a slightly different niche from the genus's giants, but the dietary template — greens and detritus first, invertebrates second — is the same.
Mating
The species is a monogamous, biparental substrate spawner that becomes territorial as a pair forms. Outside breeding it is reasonably sociable for a Vieja, but a settled pair claims and defends a territory around a chosen spawning surface, and — as throughout the genus — pairing can be combative, with a male liable to harass an unready female, so a well-matched pair in adequate space matters. Courtship follows the heroine pattern of lateral displays, jaw-locking, quivering and the joint cleaning and inspection of a flat hard surface, accompanied by the deepening of body colour and the female's increasing girth as she ripens.
Breeding
Vieja breidohri is a biparental, open substrate spawner. The pair cleans a flat hard surface and the female lays her eggs on it in the open, after which both parents share guarding and fanning; after hatching the wrigglers are typically moved to pits excavated in the substrate and the free-swimming fry are led about and defended vigorously by both parents. Specific wild fecundity figures are not well documented, but as a smaller member of the genus it can be expected to produce broods toward the lower end of the genus-typical several-hundred-fry range. In aquaria it spawns readily in the standard biparental manner given a compatible pair, a flat spawning site and a digging substrate; its more moderate size makes pair management somewhat easier than in the giant Vieja, though spawning aggression remains the limiting factor.
In the aquarium
Vieja breidohri is, by the standards of its genus, a relatively manageable large cichlid, and its modest adult size makes it a sensible choice for keepers who want a Vieja without the space demands of a 12 in fish. At around 6.5 in it still needs a substantial tank: a footprint of roughly 120 × 17.5 in (about 55 US gal) is a reasonable minimum for a single fish or a settled pair, with more space advisable if other robust cichlids share the aquarium. Water chemistry is undemanding within the natural envelope — a near-neutral to mildly alkaline pH (about 7.0–8.0), moderate hardness and a temperature of roughly 77–84 °F suit it well. Generous filtration and regular water changes keep these messy feeders in good condition; strong current is unnecessary, so aim filter returns to break the surface for gas exchange.
Use a sand or fine substrate, since the fish digs, and furnish the tank with sturdy rockwork, roots and driftwood that provide cover and break up sightlines; décor must be stable, as the fish rearranges it. As with all Vieja, rooted plants are largely futile — they uproot and eat vegetation — so greenery is best treated as food or restricted to tough species. Diet should respect the species' plant bias: spirulina and other green foods, blanched vegetables and quality vegetable-based pellets as the base, with frozen or live invertebrates as supplements rather than the staple.
Temperament is robust but more workable than in the larger Vieja simply because the fish is smaller. Outside breeding the Angostura cichlid is reasonably even-tempered and combines with other sturdy Central American cichlids of similar size and comparable tankmates able to hold their own; small or delicate fish are unsuitable. Aggression rises at spawning, when a guarding pair will dominate its territory, so ample space, broken sightlines and a contingency plan to separate fish remain sensible. As ever, the common keeper mistakes are underestimating even a 6.5 in cichlid's territoriality, overstocking and feeding too richly.
Conservation
The IUCN Red List assesses Vieja breidohri as Data Deficient (assessed 2018, published 2019), with the population trend recorded as unknown. The Data Deficient listing reflects genuine gaps in knowledge of the species' distribution, abundance and biology rather than a documented decline. The conservation context is nonetheless worth noting: the species is restricted to the Grijalva system, where — as the closely related and Endangered Vieja hartwegi shows — large dams have transformed flowing rivers into reservoirs, fragmenting fish populations, drawing development and pollution, and aiding the spread of introduced tilapia. Vieja breidohri is itself partly a fish of the Angostura reservoir, which suggests some tolerance of impounded conditions, but its narrow range in a heavily dammed and deforested basin means its security cannot be assumed. It carries no CITES listing and is harmless to humans; better field survey is needed before its status can be properly judged.