Bluestriped Butterflyfish

Bluestriped Butterflyfish

The Bluestriped Butterflyfish (Chaetodon fremblii) is a bright, golden-yellow Hawaiian endemic crossed by diagonal electric-blue stripes, with a black spot behind the head in place of the usual butterflyfish eye-band. Unusually for the family, it lacks a strong eye-mask and is one of the hardier, more adaptable butterflyfish in the hobby, which has made it a favourite for keepers who want the elegance of a butterflyfish without the extreme difficulty of obligate coral feeders.

Coming from cooler Hawaiian reefs, it appreciates slightly lower temperatures than most tropical species.

Natural Habitat & Origin

Chaetodon fremblii is endemic to the Hawaiian Islands, where it lives on coral and rocky reefs, often over rubble and mixed substrate, foraging for small invertebrates and algae. It is frequently seen alone or in pairs, ranging over the reef as it picks at the bottom.

In the aquarium it appreciates plenty of live rock for grazing and shelter, in a mature system with steady, slightly cooler water.

Care Requirements

Maintain stable marine conditions: salinity around 1.024–1.026, pH 8.1–8.4, and a temperature toward the cooler end of the reef range, around 23–25°C (73–77°F), reflecting its Hawaiian origin. Reaching about 13 cm (5 inches), it suits a tank of around 200 litres (about 55 US gallons) or more with ample rockwork. It is hardier than most butterflyfish and adapts readily to aquarium foods.

Diet & Feeding

This butterflyfish is an omnivore, feeding in the wild on polychaete worms, small invertebrates and algae rather than living coral. It usually adapts well to captivity: offer a varied diet of frozen mysis and brine shrimp, marine preparations and foods with marine algae content. Feed several small meals a day to keep it in good condition.

Behavior & Temperament

It is a peaceful, active fish that mixes well in a calm community and can be kept singly or as a pair. It rarely troubles other fish and spends much of its time foraging over the rockwork. Avoid housing it with aggressive species that will outcompete it or keep it hidden.

Tank Mates

Good companions are other peaceful marine fish — tangs, peaceful wrasses, anthias, cardinalfish and similar — that tolerate cooler water. In a reef it is relatively well behaved for a butterflyfish, but because it may occasionally nip coral polyps or invertebrates it is best described as reef-safe with caution, and is safest with hardy corals.

Breeding

Chaetodon fremblii is a pelagic spawner with planktonic larvae and is not bred in the home aquarium. Trade specimens are wild-collected from Hawaiian waters.

Common Health Issues

The Bluestriped Butterflyfish is hardy by butterflyfish standards but, like all marine fish, is susceptible to marine ich (Cryptocaryon irritans) and marine velvet (Amyloodinium ocellatum), particularly when stressed or newly imported. Quarantine new arrivals, keep water quality stable, and offer a varied diet. Given a peaceful tank and slightly cooler water, it is one of the most approachable and dependable butterflyfish for an intermediate keeper.