Taxonomy & naming
Tometes kranponhah was described in 2016 by Andrade, Jégu and Giarrizzo, and it holds the distinction of being the first species of Tometes documented from the Brazilian Shield rather than from the Guiana Shield rivers where most of its congeners occur. It belongs to Serrasalmidae — the piranha, pacu and silver-dollar family — within the order Characiformes, a family the Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats as having been extensively re-split in recent decades, with silver-dollar-type herbivores parceled out of the old catch-all genus Myleus into narrower genera including Tometes, Myloplus and Ossubtus. Tometes itself is defined by a sharp-edged, multicuspid dentition adapted to grazing rather than the blade-like predatory teeth of true piranhas.
The species epithet, "kranponhah," is not a Latin or Greek construction but comes from the Pytako, an indigenous group inhabiting the banks of the Xingu basin where the species was collected — a naming convention increasingly used by describers to credit local and indigenous knowledge of a region's fish fauna. In the aquarium trade the species has occasionally been confused with the related Xingu and Tocantins basin pacu Mylesinus paucisquamatus, and importers note the two are easy to mix up without close comparison.
Morphology
Tometes kranponhah has the classic silver-dollar profile: a deep, laterally compressed, disc-shaped body built for stability in current rather than speed, with a small terminal mouth armed with sharp, multicuspid teeth suited to rasping algae and plant tissue rather than flesh. FishBase records a maximum length of 19 in total length, making it one of the larger silver dollars in the aquarium trade — importer data cites adults closer to 15.5 in, still a substantial fish that dwarfs the small tetra-sized silver dollars many keepers picture.
A distinguishing field mark is dark pigmentation on the opercle, the bony gill cover, which helps separate it from superficially similar Xingu and Tocantins basin relatives. Mature males develop elongated filaments on the dorsal-fin rays, a sexually dimorphic trait shared with several other Tometes species and one of the few external cues to sex in this genus.
Habitat
The species is endemic to the Xingu River basin in Brazil, a major clearwater tributary of the Amazon known for its long stretches of rapids and rocky, fast-flowing channels. Tometes kranponhah is rheophilic — adapted specifically to fast-water habitat — and it is found in and around the rapids that make the middle Xingu one of South America's most distinctive river environments, rather than in the still floodplain lakes and backwaters that many other serrasalmids favor.
Detailed water-chemistry data for the species' native rapids has not surfaced in available sources, but the Xingu's rapids habitat generally means warm, well-oxygenated, moving water over rock and cobble substrate. This is a fish adapted to current, and that has direct implications for its aquarium care: still, sluggish water does not replicate the conditions it evolved for.
Feeding
Tometes kranponhah is phytophagous — a strict plant-eater — grazing algae and plant material from the rocks and vegetation of its rapids habitat in the wild. This is consistent with the genus as a whole, whose sharp, multicuspid teeth are a grazing adaptation rather than a predatory one, despite the fish's membership in the same family as the true piranhas.
In the aquarium this translates directly: a diet built around vegetable matter — blanched greens, spirulina-based flake or pellet, and algae wafers — supplemented with some protein, mirrors its natural grazing habit far better than a carnivore-oriented diet. Keepers should expect the fish to treat live aquarium plants as food rather than décor; this is not an occasional habit but the core of how the species feeds.
Mating
No courtship or spawning behavior has been documented for Tometes kranponhah in available sources — this is a recently described (2016), narrow-range species with essentially no aquarium breeding history, and even basic reproductive biology has not been published. What is documented is limited to juvenile social behavior: imported juveniles in the 2–3 in range are described as somewhat quarrelsome among themselves, with minor, generally acceptable fin damage from squabbling within the group.
Given the closely related genera in Serrasalmidae, an egg-scattering strategy over vegetation would be the expected pattern, consistent with silver dollars generally, but this has not been confirmed for this species and should not be stated as documented fact.
Breeding
There is no published breeding record for Tometes kranponhah in the hobby or in aquaculture. Silver dollars in general — the Metynnis and Myloplus lineages this species' feeding ecology and body plan resemble — are egg-scatterers that release eggs over fine-leaved plants with no parental care, and that is the plausible mode for this species by analogy, but it has not been confirmed for T. kranponhah specifically. Given the species' rarity in the trade, its large adult size and its specialized fast-water habitat, home breeding should be considered essentially undocumented rather than simply difficult.
Prospective keepers should not expect to breed this fish and should source specimens as wild or wholesale imports rather than tank-raised stock.
In the aquarium
Tometes kranponhah is a specialty import rather than a mainstream aquarium fish, and hobbyist care data remains limited. What is clear from the available sources is that this is a large, active schooling grazer: adults reach roughly 15.5–19 in, so a tank needs to be sized for a big, disc-bodied fish that wants to move, not a small planted showpiece. Keep it in a group, in a spacious tank with strong water movement and filtration echoing its native rapids habitat, and expect it to graze on any live plants offered — this is not a fish for an aquascape, but for a robust, hard-scaped setup with algae growth or prepared vegetable foods to occupy its grazing instinct.
Juveniles can show minor squabbling and fin-nipping within the group, generally regarded as acceptable background wear rather than a serious problem, but it reinforces the need for adequate numbers and space rather than isolating individuals. Because so little husbandry data exists for this species, keepers should treat it cautiously and be prepared to adapt care based on the better-documented needs of related Tometes and silver-dollar species.
Conservation
Tometes kranponhah has not been evaluated by the IUCN Red List (status: Not Evaluated), which is unsurprising for a species described only in 2016 from a single river basin. It appears to be locally abundant within its known Xingu River range, but that range is a specific concern: the Xingu has been dramatically altered by the Belo Monte hydropower dam, one of the largest and most controversial hydroelectric projects in the Amazon, which has changed flow regimes and inundated stretches of the rapids habitat this rheophilic species depends on.
No formal assessment has quantified the impact of Belo Monte on Tometes kranponhah specifically, but researchers have flagged the broader Xingu rapids fish fauna, including phytophagous serrasalmids like this one, as potentially vulnerable to the hydrologic alterations the dam has caused. Its Not Evaluated status should be read as a data gap rather than a clean bill of health.