Taxonomy & naming
Zuzana Musilová, Ingo Schindler and Wolfgang Staeck described Andinoacara stalsbergi in 2009 (Vertebrate Zoology 59:131–141) — the same paper in which Musilová and colleagues erected the genus Andinoacara for a clade of trans- and cis-Andean cichlids. The genus name fuses andino-, the Andes, with acará, the Tupí-Guaraní word for cichlids; the species sits in the rivulatus group, in subfamily Cichlinae (the Cichlasomatini of older usage). The Norwegian aquarist Alf Stalsberg collected the holotype, now held at the Senckenberg Natural History Collections in Dresden (MTD F-31782); its type locality is the Río Pisco in the Departamento de Ica, on Peru's Pacific slope, near 13°43′S, 75°59′W. The epithet honours Stalsberg (1948–2022) for his long commitment to advancing knowledge of cichlid fishes.
The name settled a confusion that had run for decades. From the early 1970s a white-edged ('Silbersaum') cichlid from Peru and a gold- or orange-edged ('Goldsaum') fish from Ecuador were both traded as 'Aequidens rivulatus' and called 'green terror.' When Werner and Stawikowski collected at Günther's Ecuadorian type locality in 1985, they found only the gold-saum form — proof that true Andinoacara rivulatus is the Ecuadorian gold-edged fish, and that the Peruvian white-saum fish was still undescribed. Musilová, Schindler and Staeck named it stalsbergi in 2009, and a third member of the group, the northern-Ecuadorian Andinoacara blombergi, was split off in 2012. The trade names remain tangled: several hobby sources reserve 'green terror' for Andinoacara stalsbergi and call Andinoacara rivulatus the 'gold/orange saum,' while FishBase and most of the trade still attach 'green terror' to Andinoacara rivulatus — so the name should always be checked against drainage and saum colour.
Morphology
Andinoacara stalsbergi is a robust, deep-bodied, laterally compressed cichlid with a large head and steep forehead, built on the same plan as its rivulatus-group relatives. FishBase gives maxima of 4.5 in standard length in males and 4 in in females, though aquarium fish of this group commonly outgrow preserved wild material. The body is metallic green to blue-green, its scales catching electric-blue and turquoise highlights, and the head and cheeks carry the fine, wavy bluish-silver streaks seen across the whole complex.
The most useful field character is the fin margin: in Andinoacara stalsbergi the dorsal and caudal fins are edged in narrow white ('silver'), whereas Andinoacara rivulatus shows a broad orange, gold or red saum. The scales offer a second clue — in Andinoacara stalsbergi each scale has a dark centre with a dark edge, while in Andinoacara rivulatus a lighter blue-green edge rings a darker centre. Scale and predorsal counts separate it from the Esmeraldas-basin Andinoacara blombergi. Sexual dimorphism is pronounced and group-typical: males grow larger and longer-finned and develop a fleshy nuchal hump on the forehead — the mark of a dominant breeding male — while females stay smaller, rounder and shorter-finned. Juveniles, before the saum colour fixes, are hard to tell from Andinoacara rivulatus, which is the root of much of the trade confusion.
Habitat
Andinoacara stalsbergi lives on the trans-Andean Pacific slope of Peru, in the coastal rivers and lakes of the desert littoral between roughly 5°S and 14°S. Its habitat is the most distinctive thing about its ecology and unusual for a cichlid: clear rivers with sand and rock bottoms and aquatic plants, turbid coastal lagoons, and genuinely brackish water — the brackish Laguna de Vegueta is among its recorded localities. The chemistry matches. FishBase records a pH of about 7.7–9.2 (markedly alkaline), a temperature band of about 73–82 °F, and a very wide hardness range from roughly 6.7 up to 40 dH. The species adapts well to very alkaline, hard, mineral-rich water and even tolerates brackish conditions, and it shares its waters with fishes such as guppies (Poecilia reticulata) and introduced tilapia. It is a demersal, bottom-oriented fish. This tolerance of hard, alkaline and partly brackish water sets it sharply apart from the soft-water Amazonian acaras — and even from its close relative Andinoacara rivulatus — and follows directly from life in the rivers and lagoons of one of the driest coastlines on Earth.
Feeding
No dedicated diet study has been published for Andinoacara stalsbergi, so its feeding ecology is inferred from its anatomy and its close relatives. FishBase estimates a trophic level of about 3.2 — an omnivore that leans toward small animal prey. Like the rest of its group, it has the conical jaw teeth and generalist pharyngeal apparatus of a substrate forager, and it can be expected to pick aquatic insect larvae, small crustaceans, worms and other benthic invertebrates from the river and lagoon bed, along with plant matter and detritus. In its coastal-river and lagoon community it works as a medium-sized, benthic-leaning omnivore. Captive fish of this group are famously unfussy, taking prepared, frozen and live foods readily — a match for an opportunistic wild diet, and part of why the group is so easy to keep.
Mating
Like the rest of its group, Andinoacara stalsbergi is a biparental, pair-forming substrate spawner, and it carries the assertive temperament that earned the complex its 'green terror' name. A male and female form a bond, jointly choose and clean a spawning surface, and defend the surrounding territory together, the metallic body and white-edged fins working as signals in lateral, fin-spreading courtship. These are competitive, strongly territorial fish. Intraspecific aggression runs high, and an unbonded male will often persecute a female he has not paired with — a behaviour well documented across the group and central to keeping them. Some keepers judge Andinoacara stalsbergi marginally more aggressive than true Andinoacara rivulatus. A genuinely bonded pair, given space, holds and defends its territory together and cooperates closely in raising young.
Breeding
Andinoacara stalsbergi is an open, biparental substrate spawner — the standard mode of its group. Most of what is known comes from aquarium observation rather than the field, since the fish has been bred in the hobby for decades under the 'green terror' label. A bonded pair cleans a flat surface — a stone, a slab or a cleared patch of substrate — and the female lays a sheet of adhesive eggs. Both parents then tend the clutch: the female fanning and directly caring for the eggs, the male patrolling and defending the perimeter. Hatched wrigglers are moved to pits and guarded, and once free-swimming the fry are herded and defended as a school by both parents, in the extended biparental care typical of the genus. No precise clutch figure has been published for Andinoacara stalsbergi, but the group spawns productively — its relative Andinoacara rivulatus lays several hundred eggs per spawn, and keepers report comparable broods — so that number is best treated as a group-typical guide. Pairs in condition spawn repeatedly at short intervals. Because Andinoacara stalsbergi and Andinoacara rivulatus look alike and will hybridise, the two should never be bred together if pure lines are wanted.
In the aquarium
Andinoacara stalsbergi has been a hobby fixture for half a century even though its own name dates only to 2009 — this is the white-saum 'green terror' long imported from Peru. It is hardy, disease-tolerant, easy to feed and easy to breed; the real challenges are spatial and social, not a matter of delicacy.
Tank. A large male reaches the top of the group's size range — 4.5 in standard length in wild material, and meaningfully larger in well-fed aquarium fish, plausibly into the high teens of centimetres total length — while females stay smaller. A single fish or a confirmed pair needs a substantial tank, on the order of 80–105 US gal with a long footprint (59 in is a realistic guide), to satisfy a strongly territorial cichlid and to dilute the heavy bioload of a big feeder. Use sand or fine-to-medium gravel, since these fish dig hard, especially before spawning, and anchor the layout with large stable rockwork, heavy driftwood and a flat-topped rock or slab for territory and an egg-laying site; only tough or potted plants survive the redecorating.
Water. This is where Andinoacara stalsbergi is easy for keepers with hard tap water: it is naturally a fish of alkaline, hard, mineral-rich coastal water and even tolerates brackish conditions. The documented field range is a pH of about 7.7–9.2, a temperature of 73–82 °F, and hardness anywhere from moderate to very high (about 6.7–40 dH). It thrives at neutral-to-alkaline pH and moderate-to-hard water and neither needs nor suits the soft, acidic regime built for Amazonian cichlids. A mid-20s Celsius temperature, generous filtration and regular water changes round out its needs.
Tankmates. The fish earns 'terror': large, competitive and strongly territorial, it will intimidate, chase and injure anything it treats as a rival, and intraspecific aggression is fiercest of all — two males without space and visual barriers will fight, and an unpaired female can be harried badly. Keep it with robust fish of similar or greater size that use different zones (other large New-World cichlids, big catfish, large plecos), and watch them closely; small or timid fish become prey or stress targets. Many keepers run it as a single fish, a single bonded pair, or in a large species tank. For breeding, offer a flat spawning surface and a genuinely bonded pair, and be ready to separate them between cycles if the female is harassed. One last identity check: fish sold as 'green terror' may be Andinoacara stalsbergi (narrow white saum), true Andinoacara rivulatus (broad orange-gold saum), or ambiguous juveniles — check the saum colour under good light, trust provenance from reputable breeders, and never mix the two, because they hybridise.
Conservation
The IUCN Red List assessed Andinoacara stalsbergi as Least Concern in September 2020. It ranges across a string of Pacific coastal rivers and lagoons in Peru spanning roughly nine degrees of latitude — a reasonably broad, if naturally fragmented, range — and it is a strikingly tolerant generalist, at home in clear rivers, turbid lagoons and hard, alkaline or even brackish water, which buffers it against disturbances that would threaten a narrow specialist. It carries no CITES listing, and FishBase rates it harmless with low fishing vulnerability. The pressures on Peru's desert-coast rivers are real all the same: these are short, heavily used watercourses draining one of the world's driest coastlines, subject to water abstraction for irrigation and cities, agricultural and urban pollution, and the presence of introduced fishes such as tilapia in many of the same waters where stalsbergi lives. None of this is documented as a population-level threat today, and the Least Concern status reflects a hardy, adaptable cichlid currently secure across the Peruvian coastal littoral — but the long-term health of its rivers depends on how those scarce desert waters are managed.