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EveryFish
A pair of Hillstream Loaches Beaufortia kweichowensis , size about 3.5 cm (left) and 5 cm (right).

Butterfly loach

A small, flat freshwater loach from fast Chinese streams.

Photo: Lerdsuwa, CC BY-SA 3.0, via Wikimedia Commons

Beaufortia kweichowensis is a small gastromyzontid loach native to the Xi River in China. It lives in fast-flowing highland streams and is popular in aquariums for its unique shape and algae-eating habits. Keepers must provide high oxygen and strong water flow to mimic its natural habitat.

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  • Grows to a maximum length of 8 cm
  • Native to fast-flowing streams in the Xi River
  • Requires high oxygen and strong water flow in tanks
  • Males often display stronger colouration than females
  • Popular aquarium fish known as Chinese hillstream loach

What it is

The butterfly loach is a species of gastromyzontid loach with a flattened body adapted for life in swift currents. It grows to a maximum total length of 8 cm. This fish is endemic to China and is widely kept in home aquariums under names such as Chinese hillstream loach or Hong Kong pleco. Its shape allows it to cling to surfaces in fast water.

Where it lives

This species is found only in China, specifically within the Xi River system. It inhabits fast-flowing highland and inland streams. These environments provide the high oxygen levels and strong currents that the fish requires for survival. The natural habitat is characterised by rocky substrates and cool, well-oxygenated water.

How it lives

In captivity, these loaches are generally not aggressive but can be territorial. They may engage in topping behaviour, where one fish attempts to cover another. These skirmishes rarely cause harm as one participant usually stops. They thrive in groups of three to seven individuals. Their small mouths require specific feeding strategies.

Breeding and life cycle

Sexual dimorphism is minimal, though males often display more intense colouration. Breeding in captivity is uncommon but possible. Reproduction may occur in pits dug under rocks if the tank environment closely mimics natural riverine conditions. Successful breeding requires careful attention to water flow and substrate arrangement.

Butterfly loach
A drawing made by EveryFish from what this page says. It is a diagram, not a picture of the real fish.

Fish and people

This fish is a popular choice for aquarium enthusiasts due to its unique appearance and behaviour. It requires a tank of at least 91 cm with strong water flow and high aeration. Algal growth should be encouraged through adequate lighting, as this forms part of its diet. Suitable plants include Anubias and Microsorum pteropus attached to rocks or wood.

Questions people ask about Butterfly loach

What size tank does a butterfly loach need?

A tank with a minimum length of 91 cm is preferable. This space allows for the strong water flow and high oxygen levels that the species requires to thrive in captivity.

Do butterfly loaches eat algae?

Yes, natural algae is part of their diet. Keepers should provide adequate lighting to promote algal growth. They also accept flakes, sinking pellets, algae wafers, and blanched vegetables like spinach.

Are butterfly loaches aggressive towards other fish?

They are not generally aggressive but can be territorial. They may engage in topping behaviour with conspecifics, where one fish covers another. These clashes seldom result in physical damage to the fish involved.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Beaufortia kweichowensis", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.

It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.

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Photo credits on this page

The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

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