Marquesas Butterflyfish

Marquesas Butterflyfish

The Marquesas Butterflyfish (Chaetodon declivis) is an uncommon and sought-after butterflyfish from the remote central Pacific. Pale and silvery with subtle yellow and dark markings, it has the clean, understated elegance typical of the plankton-feeding butterflyfish. Its rarity — tied to its limited, far-flung range — makes it a prized fish for the dedicated marine aquarist, and it is generally hardier and more adaptable than the obligate coral-feeding butterflyfish.

As a mid-water plankton feeder, it tends to be less destructive in a reef than its coral-eating relatives, though caution is still warranted.

Natural Habitat & Origin

Chaetodon declivis is found around the Marquesas Islands and nearby central Pacific reefs, where it feeds primarily on zooplankton drifting over the reef, often in pairs or small groups. Its isolated range is the main reason it is so seldom seen in the trade.

In the aquarium it appreciates open water above the rock for mid-water feeding, with live rock providing shelter and grazing surfaces.

Care Requirements

Maintain stable marine conditions: salinity around 1.024–1.026, pH 8.1–8.4, and a temperature of about 24–26°C (75–79°F). Reaching about 14 cm (5.5 inches), it suits a tank of around 280 litres (about 75 US gallons) or more with open swimming space and plenty of rockwork. A mature, stable system and a peaceful environment suit this elegant fish best.

Diet & Feeding

The Marquesas Butterflyfish is a planktivorous omnivore, feeding on zooplankton in the wild along with some small invertebrates. It generally adapts well to captivity: offer a varied diet of frozen mysis and enriched brine shrimp, marine preparations and foods with marine algae content, fed in frequent small amounts to suit its mid-water grazing.

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 feeding in open water. 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. In a reef, treat it with caution: although a plankton feeder rather than a dedicated corallivore, it may occasionally sample coral polyps or invertebrates, so it is safest in fish-only systems or reefs with hardy corals.

Breeding

Chaetodon declivis is a pelagic spawner with planktonic larvae and is not bred in the home aquarium. Trade specimens are wild-collected from its remote range, contributing to its scarcity.

Common Health Issues

The Marquesas Butterflyfish is reasonably hardy for a butterflyfish 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 a mature system, it is an elegant and rewarding rarity for an experienced keeper.