Butterfly Loach (Sewellia breviventralis)

Family: Balitoridae

Butterfly Loach — a Balitoridae from Vietnam, peaceful grazer; squabbles are brief pushes. Reaches 3.8–5.6 cm; loosely social; crowding causes endless pushing. 18–26 °C.

Care parameters

Water temperature
18–26 °C
pH
6.5–7.5
GH hardness
5–15 dGH
Adult length
3.8–5.6 cm
Minimum tank
38 L
Water layer
Bottom-dwelling
Difficulty
Moderate
Temperament
Peaceful grazer; squabbles are brief pushes
Origin
Vietnam

Species overview

A Balitoridae species native to Vietnam: Sewellia breviventralis lives bottom-dwelling over fast-flowing mountain streams, clinging to rocks. Peaceful grazer; squabbles are brief pushes. Adults reach 3.8–5.6 cm. It is one of the aquarium-kept Sewellia species we profile, alongside Sewellia lineolata, Sewellia albisuera.

Native biotope

Habitat
Fast-flowing mountain streams, clinging to rocks
Flow
Very strong, highly oxygenated current
Dissolved O₂
Requires very high dissolved oxygen

Aquascape & hardware

Substrate
Bare rock and coarse gravel
Hardscape
Large smooth boulders
Plants
Minimal; algae-covered stones instead

Temperament, diet & tankmates

Schooling
Loosely social; crowding causes endless pushing
Diet
Algae and biofilm specialist; supplement with wafers
Recommended tankmates
  • Other cool-water stream fish — Share the need for oxygen and flow
Avoid keeping with
  • Large aggressive cichlids — Disrupt the calm grazing regime

Breeding & notes

Sexual dimorphism
Difficult to distinguish
Breeding method
Breeding rarely reported in aquaria; presumed egg-scatterer

Frequently asked questions

Is Butterfly Loach easy to keep?

A moderate-level species: peaceful grazer; squabbles are brief pushes; stable water matters more than fancy equipment.

What temperature and water chemistry does Butterfly Loach need?

Set the heater to 18–26 °C and avoid swings. pH 6.5–7.5, GH 5–15 dGH suit it.

How big does Butterfly Loach get, and what tank size?

Full size is 3.8–5.6 cm. Minimum tank: 38 L, with open swimming space along its bottom-dwelling habits.

What does Butterfly Loach eat?

Algae and biofilm specialist; supplement with wafers. Vary the menu — quality flakes or pellets plus frozen or live foods.

Can Butterfly Loach live with other fish?

Peaceful grazer; squabbles are brief pushes. Recommended tankmates: Other cool-water stream fish — Share the need for oxygen and flow. Avoid Large aggressive cichlids — Disrupt the calm grazing regime.

Where does Butterfly Loach come from?

Comes from Vietnam: fast-flowing mountain streams, clinging to rocks. Expect very strong, highly oxygenated current and requires very high dissolved oxygen.

How does Butterfly Loach breed?

Breeding rarely reported in aquaria; presumed egg-scatterer. Difficult to distinguish.