Rosy Loach (Petruichthys sp. 'Rosy')

The Rosy Loach (Petruichthys sp. 'Rosy'), also referred to informally as Yunnanilus sp. 'Rosy', is a small and endearing loach from slow-moving streams and rice paddies of Myanmar. Growing to only 2–3 cm, it is one of the smallest loaches available in the hobby and is perfectly suited to nano planted aquariums. Its warm, sandy-rosy body with scattered small dark spots gives it a soft, appealing appearance quite different from most other loach species.

Rosy Loaches are active during the day and display curious, social behavior, often seen investigating every corner of the tank together in loose groups. Unlike some loaches, they are not strictly nocturnal and spend considerable time in the open, especially in tanks with sufficient cover. They occupy the mid to lower water column and are frequently seen picking at the substrate and plant leaves for biofilm and small organisms.

This species is peaceful with all other fish and is too small to pose any threat to tankmates. It thrives in groups of 10 or more where individuals feel secure and express natural social behavior. Their small size and gentle nature make them excellent companions for dwarf shrimp (Neocaridina, Caridina) and other nano fish.

Rosy Loaches prefer soft to moderately hard, slightly acidic to neutral water with gentle flow. A densely planted tank with fine substrate, leaf litter, and small hiding spots creates ideal conditions.

Water Parameters: Rosy Loaches prefer pH 6.5–7.5, temperature 20–26°C, GH 5–15. Soft to moderately hard, slightly acidic to neutral water is ideal. They are from cool, slow-moving waters so avoid high temperatures. Gentle filtration is appropriate.

Tank Setup: A 20–30 liter nano aquarium for a group of 10. Use fine sand substrate, leaf litter (Indian almond leaves), small driftwood pieces, and dense planting with mosses and fine-leafed plants. Gentle flow from a sponge filter or small internal filter is ideal. Avoid strong current.

Feeding: Microinvertebrate pickers that do well on micro flake food, micro pellets, baby brine shrimp, micro worms, and daphnia. They also graze biofilm from surfaces. Feed in small amounts twice daily with fine foods appropriate to their tiny size.

Tankmates: Excellent nano community fish. Safe with all small peaceful fish, dwarf shrimp (they are too small to eat adult shrimp), and snails. Keep with nano rasboras, ricefish, and small tetras. Avoid large or boisterous fish that will outcompete them for food.

Health: Generally hardy in appropriate cool, gentle conditions. Sensitive to high temperatures. Maintain stable parameters and gentle current. Weekly small water changes of 20–25% keep the nano tank healthy.