Taxonomy & naming
Cichla melaniae was described by Sven O. Kullander and Efrem J. G. Ferreira in 2006 as one of nine new species in their comprehensive review of the South American peacock-bass genus Cichla (Ichthyological Exploration of Freshwaters 17(4): 289–398). The genus name comes from the Greek kichle, an old word for a wrasse; the species epithet honors Melanie L. J. Stiassny, the curator of fishes at the American Museum of Natural History and a prominent cichlid systematist. The type locality is the lower Rio Xingu in Pará, Brazil, and the nomenclatural act is registered in ZooBank.
Cichla sits in the subfamily Cichlinae, tribe Cichlini — the New World cichlids — and is the only peacock-bass genus, distinct from the dwarf and eartheater cichlids that share its rivers. In English the fish is sold as the Xingu or "Fogo" peacock bass; in Brazil, like its congeners, it is simply a tucunaré. Kullander and Ferreira separated it from the superficially similar Cichla mirianae of the Tapajós and Teles Pires drainages on fine characters: melaniae lacks the pale spots on the side of the head and the large mid-lateral ocelli of mirianae, and carries more scales in a key lateral row (78–85 versus 72–80).
Morphology
This is a fusiform, torpedo-shaped predator built the way all peacock bass are built — a large oblique mouth, a projecting lower jaw, and a dorsal fin notched into spiny and soft halves. The defining markings, per the original description, are a set of three narrow dark vertical bars on a greenish flank, frequently with additional narrow bars (the "1a" and "2a" bars in Kullander and Ferreira's notation) intercalated between them, and a scattering of numerous minute white spots across the body, many of them ocellated (pale centers ringed in dark). Juveniles wear a complete dark lateral band that breaks up with age, and the lateral line is interrupted rather than continuous. As in the genus generally, breeding and dominant adults intensify, the spots and bars sharpening against a darker, more contrasting ground.
Size is where reports diverge, and it is worth being precise. Kullander and Ferreira's material was modest: the IUCN account, drawing on the description, cites a mean body length around 7.5 in (7.5 in), and FishBase lists a maximum of about 14 in (14 in) total length and 1.6 lb (710 g) — small for a peacock bass. Aquarium and sport-fishing sources routinely claim 15 in (15 in) or more for well-fed specimens, which is plausible for a captive fish but outruns what the type series documented. The honest summary: the wild fish examined by its describers was a comparatively small Cichla, and larger figures in the hobby trade should be read as anecdote rather than measured maxima.
Habitat
Cichla melaniae is endemic to the Rio Xingu in Pará, Brazil, concentrated in the lower and middle reaches of the drainage. The Xingu is the Amazon's largest clearwater tributary — a bedrock river running over the ancient crystalline shield of central Brazil, with low conductivity, soft water, and (away from sediment) good visibility. Its signature feature is the Volta Grande, a roughly 80 mi (81 mi) stretch of rapids and braided, anastomosing channels whose habitat heterogeneity supports an extraordinary endemic fish fauna; surveys of the rapids list Cichla melaniae among the rheophilic (current-loving) species characteristic of the upper and middle Volta Grande (Fitzgerald et al., Biological Conservation 222, 2018).
The in-situ measurements that exist are telling. Fish collected at Balneário do Pedral were in shallow water (FishBase records a depth range of roughly 0–3 ft / 0–3 ft) with strong current among lava rocks, at pH 6.5, less than 1 dGH (very soft), and a warm 86–90°F (86–90 °F). This is not a placid backwater cichlid: it is a fish of swift, well-oxygenated, hard-substrate channels — the same fast water that, until recently, defined the Volta Grande and that the river's hydrology has now largely lost below the dam.
Feeding
Peacock bass are the apex small-bodied piscivores of South American rivers, and Cichla melaniae is no exception. FishBase places the genus at a trophic level around 4.1 — squarely a fish-eater. Across the genus, the diet is dominated by other fishes: where several Cichla coexist they partition habitat and prey, but the staple is small open-water and rocky-shore fishes — tetras (characids) and the like — taken by a fast lunge from ambush or open pursuit (Winemiller and colleagues' work on Cichla feeding ecology). Larger individuals take correspondingly larger prey, including the abundant loricariid catfishes and other rapids dwellers that share its bedrock.
Within the Volta Grande, melaniae is one strand of a tightly woven, current-driven community. The rapids' food web is unusually dependent on benthic algae and on the river-weed Podostemaceae and the invertebrates living among it — basal resources that feed the herbivores and detritivores on which a predator like Cichla ultimately depends. That dependence is precisely why disrupting the flow regime reverberates up to the top of the food chain.
Mating
Like all Cichla, Cichla melaniae is a substrate spawner with biparental care — a very different reproductive strategy from the mouthbrooding African rift-lake cichlids. Reproduction begins socially: peacock bass are gregarious as juveniles and become more territorial and intolerant as they mature and pair off, a transition keepers see clearly in tanks. A pair forms, clears and defends a territory, and prepares a cleaned hard surface for spawning.
In the rapids, the timing of pairing and spawning is almost certainly tied to the river's flood pulse — the seasonal rise, flood, ebb and drought that orchestrates breeding and migration for Amazonian fishes. That coupling of reproduction to the natural hydrograph is one more reason the altered flow regime below Belo Monte matters: change the cue, and you risk the spawning season that depends on it. Specific courtship observations for melaniae in the wild are thin, but the pattern is consistent across the genus.
Breeding
Once a pair has formed and a site is prepared, Cichla melaniae spawns as a biparental substrate brooder. The female deposits adhesive eggs on the cleaned hard surface, the male passes over and fertilizes them, and both parents then guard the eggs and, after hatching, the free-swimming fry — shepherding the school as a tight cloud and driving off intruders. This intense, shared brood-guarding is well documented across Cichla, and it is the behavior that aquarists who have spawned peacock bass describe in captivity: a defended pit, a guarded wriggler mass, and parents that herd the fry school for weeks.
Species-level breeding data for melaniae in the wild remain sparse, but nothing about it departs from the genus pattern — adhesive demersal eggs on a substrate, no mouthbrooding, and prolonged biparental care of an actively guarded fry school. In the rapids, recruitment depends on that care surviving the seasonal flood pulse, which is why the dam-altered hydrograph below Belo Monte is a long-term concern for the species' reproduction even though the adults themselves remain common.
In the aquarium
This is a monster-fish-keeper's cichlid, not a community fish, and it should be approached as such. It is also rarely available: a narrow-range Xingu endemic that enters the ornamental trade only in small numbers, usually as wild imports. Even at the conservative wild size it is a fast, aggressive, intensely predatory animal; experienced keepers raise Cichla in groups of three or more, because lone or paired fish tend to become insecure, withdrawn bullies, while a small shoal spreads aggression and keeps the fish out and confident. Wild-caught imports often arrive thin and parasitized, so a quarantine-and-deworm period and patient pellet-training (weaning off live and frozen food onto prepared diets) are standard advice — live feeders are best avoided, since they import disease and foul water. Warm water in the mid-80s°F (around 84–88 °F), strong filtration and current, and very large tanks are non-negotiable; the rule of thumb on the forums is that even the smaller peacock bass need long footprints, and that a growout tank is only ever temporary.
The common keeper mistakes are predictable: buying a "cute" 2 in juvenile without a plan for its adult size and appetite, housing it with anything small enough to swallow, and under-filtering a fish that eats and excretes heavily. Cichla melaniae's appeal is genuine — the green-and-black coloration and the white spangling are striking — but it is a specialist's project that demands space, filtration, and realistic tankmate choices, not a beginner's centerpiece.
Conservation
Cichla melaniae was assessed by Brazil's Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) for the IUCN Red List as Least Concern (assessment dated 7 November 2018, published 2022). The reasoning is straightforward: the species is endemic to Brazil but widely distributed and frequent-to-abundant through the middle Xingu, with no significant species-level threats detected and a population trend judged stable. It is taken locally and nationally as a food fish and enters the international ornamental trade, but neither pressure is considered to threaten the population, and CITES does not list it. On its own terms, this is not a fish in trouble.
The honest qualifier is that the river it lives in is. The Volta Grande sits at the heart of the Belo Monte hydroelectric complex, which since 2016 has diverted on the order of 70% of the Xingu's flow away from this stretch into reservoirs and canals, leaving a "reduced flow" reach where the natural flood pulse no longer arrives on time or at volume (Fitzgerald et al. 2018; reporting and monitoring summarized by Mongabay, 2025). The rapids that define Cichla melaniae's habitat are exactly what such impoundments degrade — slower water, sedimentation that fills the interstitial rock, higher temperatures, lower dissolved oxygen, and the loss of seasonal flooding that cues reproduction. Independent monitors in the reduced-flow reach have reported widespread fish deformities and decline, and the wider Xingu fauna includes genuinely imperiled rapids endemics (the critically endangered zebra pleco, Hypancistrus zebra, among them) whose fate shows how exposed this community is.
So the accurate framing is a careful one: Cichla melaniae itself is Least Concern, a relatively adaptable predator that has not, on current evidence, collapsed — but it is a narrow-range Xingu endemic whose core habitat has been fundamentally altered by a dam, and whose long-term status is tied to how (and whether) an ecological flow is restored to the Volta Grande. Least Concern does not mean unaffected, and for this fish the distinction is the whole story.