L011 Red Fin Thresher Pleco 'Pará' (Aphanotorulus emarginatus)

Common Name

Red Fin Thresher Pleco, L011 and L035, Pará locality

Scientific name

Aphanotorulus emarginatus   |   Trade name often listed as Squaliforma emarginata

Origin and Habitat

These fish are collected in the Pará State, most often collected in the Rio Pará. Amazon basin native with many regional forms. In these stretches the water runs clear, warm, and well oxygenated over sand, rock, and submerged roots. Fish shelter among crevices and roots by day, then move to open margins and sand bars at dusk to feed. Related L011 and L035 populations are documented from Xingu near Altamira and the Araguaia just above its confluence with the Tocantins, while Pará records include the Rio Trombetas and Rio Pará proper. Locality matters because pattern and fin edging can vary with river.

Temperature and Water Conditions

Aim for 77 to 82 F, which is 25 to 28 C. Wild pH is typically mildly acidic to near neutral, about 6.4 to 7.5. Strong aeration, steady current, and spotless filtration are more important than chasing exact numbers. Save any parameter tweaks for special breeding attempts. Stable, clean, oxygen rich water is the foundation for long term success.

Appearance and Size

A streamlined, long tailed pleco with the classic thresher look. The lower lobe of the tail extends and the fins often carry a red to orange margin that gives the common name real meaning. Base color is tan to brown with fine darker spotting, intensity changes with mood and with locality. Adults in aquaria commonly reach about 15 to 20 cm total length, roughly 6 to 8 inches, with larger records in some references.

Diet in the Wild

Omnivore with a strong grazer habit. It picks at algae, biofilm, and detritus on wood, rock, and sand margins, and supplements this with small invertebrates as available. Night feeding along sand banks is common.

Feeding in Captivity

Offer a varied plant leaning menu. Use quality sinking wafers and pellets with spirulina or other algae ingredients, plus blanched vegetables such as zucchini and cucumber. Add small portions of protein like bloodworms or finely chopped shellfish a few times per week, but keep the emphasis on greens and biofilm. Provide wood and hard surfaces to graze between feedings so the fish can display its natural foraging behavior.

Behavior and Tank Setup

Generally peaceful with midwater community fish, but may posture with similar shaped bottom dwellers when adult. Give open lanes for swimming and multiple retreats. A riverbank layout suits them well, with sand or fine rounded gravel, stacked rock, sturdy wood, and brisk, oxygen rich flow. Dim light or shaded zones help them display confident foraging and the red edging shows best under softer lighting.

Breeding

Rarely documented in the hobby and considered difficult. Reports suggest cave spawning with male egg guarding, similar to related hypostomine plecos. If attempting, provide several snug single entrance caves in current, condition adults on a rich but balanced diet, and keep water near the warm end of the range with very high oxygen and immaculate cleanliness. Expect a long courtship. Once eggs hatch the fry absorb yolk before taking finely powdered vegetable based wafers, crushed sinking pellets, and small live or frozen items in moderation.

Quick Facts

• Scientific name: Aphanotorulus emarginatus, frequently sold as Squaliforma emarginata
• L numbers: L011 and L035 are both used for regional forms in this group
• Locality: Pará State in Brazil, most often the Rio Pará, with other documented populations in nearby clearwaters
• Adult size: commonly about 15 to 20 cm total length, roughly 6 to 8 inches
• Temperature: 77 to 82 F (25 to 28 C)
• Wild pH: about 6.4 to 7.5
• Temperament: peaceful to assertive with similar bottom dwellers
• Diet: omnivorous grazer, algae and biofilm with small invertebrates
• Breeding: rarely reported, presumed cave spawner with male care

Tropical Fish Co. Notes

We love this fish because it reminds us of a dwarf cactus pleco. Sleek lines, a bold tail sweep, and that red fin edging create real presence without the footprint of the giant show plecos. Labeling by locality helps collectors keep the look consistent. Give it current, oxygen, clean water, and a plant forward menu with modest protein, and it settles into confident dusk patrols that bring a slice of Pará riverbank right into your aquascape.