Lord Sauron's Silver Dollar 'Rio Xingu' (Myloplus sauron)

Common Names

Thin Bar Silver Dollar, Sauron Silver Dollar

Scientific name

Myloplus sauron

Origin and Habitat

Native to Brazil’s Xingu River basin, including clear, fast, highly oxygenated reaches of the main river and rocky tributaries such as the Iriri, Culuene, and Bacajá. This is a current loving species that cruises midwater over granite, cobble, and coarse gravel in bright, clearwater conditions. It has not been recorded below the Volta Grande do Xingu rapids. Habitat alteration in parts of the basin is a conservation concern, so accurate locality labels matter.

Temperature and Water Conditions

Target 75 to 82 F, 24 to 28 C. Wild pH is commonly mildly acidic to near neutral, often about 6.0 to 7.2 in clearwater with low to moderate mineral content. Provide strong aeration and vigorous flow with excellent filtration. We do not recommend chasing exact numbers in general aquaria. Stable, clean conditions are far more important, with parameter tweaks reserved for specialized breeding or research projects.

Appearance and Size

A deep, disc shaped pacu with a crisp vertical black bar on the flank and orange to amber highlights in the fins. Males often develop longer fin filaments and stronger color, females are rounder and more subdued. The name Sauron honors the Eye of Sauron from The Lord of the Rings. The tapered black bar and orange accent together resemble that iconic eye. In the formal description series, examined individuals reached about 163.5 mm standard length, roughly 16.4 cm or about 6.5 inches, with total length somewhat longer. Closely related species in the genus Myloplus are documented to reach 30 to 40 cm total length, so plan space generously for long term groups.

Diet in the Wild

Primarily herbivorous. Field data categorize the species as a plant material feeder that grazes leaves, seeds, and fruits carried along high energy channels, with incidental invertebrates taken as encountered.

Feeding in Captivity

Offer a quality vegetable based pellet as the staple. Supplement with blanched greens like spinach, romaine, zucchini, cucumber slices, shelled peas, and spirulina wafers. High fiber gel foods are excellent for variety. Use modest portions and strong filtration so water stays pristine. Expect exploratory nibbling on tender live plants, so build the aquascape with hardy epiphytes and robust wood and stone.

Behavior and Tank Setup

A powerful midwater shoaler that relaxes in a proper group. Keep five or more when space allows so social energy stays within the school. Provide a long tank with strong directional flow, rounded stones, sturdy wood, and open lanes for cruising. Use robust filtration, high oxygen, and tight lids. Juveniles can begin in a four foot footprint, adult groups deserve six feet or more with river style flow.

Breeding

Home aquarium spawnings are not well documented yet for this newly described species. Close relatives spawn during rising water in open water or along margins and do not show parental care. Realistic attempts would involve very large, warm, ultra clean systems with strong flow, seasonal conditioning on high fiber greens with carefully balanced protein, and an expectation that success will be rare outside ponds or commercial scale setups.

Quick Facts

• Scientific name: Myloplus sauron
• Origin: Xingu River basin in Brazil, including Iriri, Culuene, and Bacajá tributaries
• Adult size: specimens in the type series to about 16.4 cm standard length, total length longer; related species in the genus can reach 30 to 40 cm total length
• Temperature: 75 to 82 F (24 to 28 C), strong oxygen and flow recommended
• Wild pH: commonly about 6.0 to 7.2 in clearwater with low to moderate minerals
• Temperament: peaceful but powerful shoaling fish that needs room
• Diet: primarily herbivorous, accepts vegetable based prepared foods with greens
• Breeding type: likely seasonal broadcast or margin spawner with no parental care, home successes not established

Tropical Fish Co. Notes

This fish wears its lore on its side. The vertical bar and orange glow read like a river lit Eye of Sauron, and a tight school looks cinematic in a bright, high flow tank. Think silver dollar energy with cleaner lines and more current. Give them room, greens, and a steady river, and you get a living coin roll of silver and orange every time they surge together.