Fish
Butterfly Barb
Enteromius hulstaerti
Origin: Central Africa: Democratic Republic of Congo (middle Congo River basin — Momboyo, Tshuapa, and Lomami rivers)
Also known as: Hulstaert's barb, African butterfly barb
Fact sheet
- Size
- 4 cm
- Lifespan
- 3 years
- Minimum tank size
- 30 L
- Temperature
- 22–26 °C
- pH
- 6–7
- Hardness GH
- 2–10 °dH
- Temperament
- Peaceful
- Social behavior
- Schooling
- Swimming zone
- Middle
- Diet
- Omnivore
- Jumps out
- Yes
- Eats plants
- No
Varieties
Overview
The butterfly barb (Enteromius hulstaerti) is one of the smallest African barbs of the family Cyprinidae, reaching only 3–3.5 cm in length. The species inhabits slow-moving, shallow, and densely shaded forest streams in the central Congo basin, where the water is extremely soft, acidic, and rich in humic substances. The fish was described by a Belgian researcher and subsequently named in honor of Gustaaf Hulstaert — a missionary monk, botanist, and entomologist who worked in the Belgian Congo and collected the type specimen. After a 25-year absence from the trade, the species resurfaced in the market around 2006 and is still considered a rare find. The fish attracts aquarists with its unusual spotted pattern, delicate finnage, and miniature dimensions, making it ideally suited to nano aquariums.
Appearance
The body is small, deep, and almost rhomboid in outline, reaching 3.5 cm in length. Coloration is creamy-golden with characteristic dark spots: a large rounded blotch in the mid-body and spots at the caudal fin base. The dorsal fin is tall; all fins are semi-transparent with a yellowish tint. The contrasting spotted pattern and fin shape genuinely resemble a fluttering butterfly. Males are slightly slimmer than females; mature females have a noticeably more rounded abdomen.
Care
An ideal fish for nano aquariums from 30–40 liters. Water must be soft and acidic: pH 5.0–6.5, hardness up to 5 dGH, temperature 22–25°C. Provide cover from rhizomes, driftwood, leaf litter, and dense vegetation. Partial shade, a dark substrate, and blackwater conditions with humic acids (peat extract or Indian almond leaves) replicate natural conditions and reduce stress. Keep a tight-fitting lid on the tank — the fish are capable jumpers.
Feeding
The butterfly barb is a micro-predator that in nature feeds on small zooplankton, insect larvae, and tiny crustaceans. In the aquarium it accepts small live and frozen foods: brine shrimp nauplii, micro-worms, daphnia, and cyclops. Some individuals can gradually be trained to accept quality micro-pellets, but live foods are strongly preferred. Particle size must be appropriate for the fish's tiny mouth.
Compatibility
The butterfly barb is a peaceful fish suitable for nano aquariums alongside other miniature African species that tolerate soft, acidic water: small characins, killifish, and nannostomus. It should not be kept with large or boisterous fish that will outcompete it for food or harass it. Keeping a school of 8–10 individuals is optimal.
Breeding
Spawning is communal; the fish scatter eggs among fine-leaved plants and moss clumps. Raise water temperature slightly to 25–26°C, pH 5.5–6.0. The female deposits a modest number of eggs among plants; adults readily eat their own spawn, so a breeding tank with a mesh separator is recommended. Larvae hatch in 24–36 hours and become free-swimming after 2–3 days. Starter foods are infusoria and the smallest brine shrimp nauplii.
Fun facts
The butterfly barb earned its common name from its contrasting spotted pattern and fin shape, which resemble butterfly wings. The species is one of the few African barbs adapted to the extremely soft, acidic blackwaters of the Congo forest wetlands. The fish was 'lost' to the aquarium hobby for nearly a quarter century, reappearing in the trade only in 2006.