Butterfly Hillstream Loach

Looks how to spot one

Flattened hillstream loach

Shaped a little like a tiny stingray: very flat and rounded when seen from above, with broad pectoral fins and pelvic fins joined into one large sucker disc that holds it fast to rocks. Females are broad and heavy-framed; males are slimmer with a squarer snout.1

Personality what they are like

Gentle and unhurried. Males claim small patches of rock, while females tend to gather where the current is strongest; squabbles are short and harmless.1

Daily activity how busy a day looks

Spends its day clinging to stones and glass and slowly grazing. It needs strong, well-oxygenated flow to feel at home; Seriously Fish recommends a turnover of 10 to 15 times the tank volume per hour.1

Grooming and care the hands-on bits

Water: 16 to 24 C, pH 6.5 to 8.0, hardness 2 to 15 dGH. Clean, clear, oxygen-rich water with strong flow, oversized filtration and regular partial water changes. A cooler subtropical fish that does not need heated water in most homes.1

Home where they are happiest

A stream-style tank with a base of at least 60 x 30 cm (about 54 litres), smooth rocks, pebbles and sand, bright light so biofilm grows, and powerheads for current. A tight lid is wise because these fish can climb glass.13

Food basics what goes in the bowl

Mainly grazes biofilm and algae with the tiny organisms living in it. In captivity it accepts sinking dried foods, vegetable-based preparations and small frozen foods such as bloodworm.1

Company who they like around

Found in loose groups in nature; Seriously Fish suggests buying six or more. Suits peaceful tankmates that enjoy cooler, fast-moving water.1

The story where it all began

Fang described the fish in 1931, at first as a form of Gastromyzon. It has since become one of the most widely kept hillstream loaches and is often sold under the trade name Hong Kong pleco, even though it is a loach rather than a catfish.1

Recognised by the official bits

IUCN Red List

Least Concern (assessed 28 April 2023)2

Taxonomy

Described by Fang in 1931, originally placed under Gastromyzon; a second subspecies, B. k. gracilicauda, is recognised from other river systems1