Taxonomy & naming
Myloplus tiete was described by Carl H. Eigenmann and Albert Norris in 1900, taking its species epithet directly from the Tietê River in southeastern Brazil, a major tributary of the upper Paraná system where the species was collected. It belongs to the family Serrasalmidae — piranhas, pacus and silver dollars — within the order Characiformes, and to the genus Myloplus, one of several silver-dollar lineages that were split out of the old, catch-all genus Myleus as serrasalmid taxonomy was revised; the Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the reference for the currently valid combination, and any older literature or trade material citing this fish under "Myleus tiete" reflects that pre-split classification rather than a distinct species.
Myloplus is a genus of round-to-diamond-bodied, laterally compressed silver dollars distinguished from the true piranhas of Serrasalmus and Pygocentrus by a single row of blunt, molariform to incisor-like teeth adapted for shearing plant material rather than flesh. Reliable identification of Myloplus tiete against its many close relatives rests on fin-ray counts, dentition detail and precise locality, all of which are best confirmed against a current, authority-level source rather than photographs alone.
Morphology
Myloplus tiete has the classic silver-dollar profile: a deep, strongly laterally compressed, roughly disc-shaped body with a small head and a gently sloping forehead, built for holding station and manoeuvring in current rather than for pursuit. FishBase records a maximum size of 6.5 in standard length, a modest figure that keeps this species well within reach of a large home aquarium compared to some of its bigger serrasalmid relatives.
Colouration follows the wider silver-dollar pattern — a bright, reflective silver body that catches and scatters light as the fish moves in a group, with the fins and body markings of individual specimens varying somewhat with age, mood and population. As with other Myloplus and Metynnis species, the flattened, disc-like body shape is itself a functional adaptation, letting the fish turn tightly among snags and vegetation while presenting a narrow profile from the front.
Habitat
Myloplus tiete is documented from the Paraguay-Paraná river basin of South America, with its type locality on the Tietê River, a major tributary system draining into the upper Paraná in southeastern Brazil. FishBase describes the species as a tropical, benthic-pelagic freshwater fish, consistent with a mid-water to bottom-associated life in river channels and their associated habitats rather than deep, still lakes.
The Paraná system spans a considerable latitudinal range, and its upper reaches run measurably cooler and more seasonal than the classic warm, stable Amazon lowlands — a point worth keeping in mind when setting up water for this species rather than defaulting to the warmest end of typical Neotropical aquarium ranges. The cache used for this article does not report specific pH or hardness figures for Myloplus tiete; keepers should treat published South American serrasalmid ranges (soft to moderately hard, mildly acidic to neutral) as a reasonable starting point rather than a documented fact for this exact species.
Feeding
FishBase describes Myloplus tiete as omnivorous, with a diet primarily built around plant material but supplemented by animal matter — the same broad feeding strategy seen across the Myloplus/Myleus silver-dollar lineage, which grazes algae, soft aquatic vegetation, fallen fruit and seeds along its home rivers, taking insects and other small prey opportunistically rather than as a primary food source.
In the aquarium this translates directly into a vegetable-forward diet: blanched vegetables such as courgette, cucumber and spinach, spirulina flake or wafers, and quality algae-based pellets should form the bulk of feeding, with occasional protein (bloodworm, brine shrimp, quality flake) offered as a supplement rather than a staple. Keepers should expect a Myloplus in a planted tank to treat live plants as food, not decor — this is not a species that can be trusted around anything but the toughest, least palatable aquarium plants.
Mating
Specific courtship behaviour for Myloplus tiete is not documented in the sources available for this article. Across the wider silver-dollar group (Myloplus and the related genus Metynnis), spawning is generally associated with a well-conditioned group, warmer temperatures and softer, more acidic water — conditions that in the wild would track the onset of the rainy season — with pairs or small groups becoming noticeably more active around fine-leaved plants or plant-like spawning mops as they near readiness.
External sexual dimorphism is not documented for this species in the available sources; keepers of related silver dollars typically report only subtle differences in body depth or fin shape between the sexes, and pairs are more often identified by behaviour than by appearance. Given the data gap, prospective breeders should treat any specific sexing guidance for this species as unconfirmed rather than assume it matches better-known Metynnis species.
Breeding
Myloplus tiete belongs to a group — the Myloplus/Metynnis silver dollars — whose typical reproductive mode is egg-scattering over fine-leaved plants or spawning mops, with no parental care of the eggs or fry afterward. This is consistent with FishBase's note that related Myloplus species are not established in captive breeding, and it should be read as an honest caution: this is not a fish with a well-worked-out home-breeding protocol, and most individuals in the trade are likely to be wild-collected or farmed rather than hobbyist-bred.
Where silver dollars of this general type have been spawned in captivity, breeders describe conditioning a group on a rich, plant-heavy diet, then softening and acidifying the water slightly to encourage a scatter-spawning event over fine plants; the adhesive-to-semi-adhesive eggs receive no guarding from the parents, who will readily eat their own eggs if not removed or separated. Given the scarcity of documented breeding reports specific to Myloplus tiete, this account should be treated as a description of the group's general reproductive strategy rather than a confirmed record for this exact species.
In the aquarium
Myloplus tiete tops out at a manageable 6.5 in standard length, but its deep, disc-shaped body and shoaling nature still call for real swimming space — a long, wide-footprint aquarium with open water in the middle, rather than a small or heavily obstructed tank. Like other silver dollars, it is a schooling fish and should be kept in a proper group of five or more; a lone or thinly-kept specimen is a stressed fish that is far more likely to nip fins or sulk than a settled group in adequate space.
The single most important care note for this species is honesty about plants: Myloplus tiete is a committed herbivore that will graze soft, fine-leaved and tender aquarium plants to bare stems within days. This is a fish for a robust, hard-scaped setup — driftwood, smooth river rock, tough floating cover — not a delicate aquascape. Water should be filtered strongly to handle a plant-heavy, high-fibre diet and its associated bioload, and given the upper Paraná's cooler, more seasonal character relative to Amazon lowland rivers, keepers should avoid defaulting to the very top of typical tropical temperature ranges without more specific confirmation.
Conservation
Myloplus tiete is assessed by the IUCN Red List as Near Threatened globally, and it carries a national Endangered assessment within Brazil — a notably more urgent status than many of the wide-ranging, heavily farmed serrasalmids in the aquarium trade, and one that reflects real, documented pressure on its native Paraguay-Paraná habitat rather than a data-poor default listing.
The upper Paraná and its tributaries, including the Tietê, have been heavily modified by damming, urbanisation and water-quality degradation across southeastern Brazil, and those pressures are the most plausible drivers behind the species' elevated national conservation status. Prospective keepers should treat any wild-collected stock of this species with that context in mind, and prefer captive-bred or farmed silver dollars where available, given that captive breeding of Myloplus tiete specifically is not established.