Aiptasia-eating Filefish

Aiptasia-eating Filefish

The Aiptasia-eating Filefish (Acreichthys tomentosus) — also called the bristletail or matted filefish — is a small, cryptic reef fish best known for one valuable habit: it eats Aiptasia, the pest anemones that plague many reef tanks. Mottled in greens and browns, with the ability to rapidly shift colour and skin texture to blend into its surroundings, it is an understated but genuinely useful member of a clean-up crew.

It is not a perfect saint, however. Once the Aiptasia runs out, this opportunistic feeder may turn its attention to coral polyps and other invertebrates, so it is best thought of as a targeted pest-control fish rather than a guaranteed-safe reef resident.

Natural Habitat & Origin

Acreichthys tomentosus is found across the Indo-West Pacific, from Sri Lanka through Indonesia and the Philippines to Tonga. It inhabits shallow coral reefs and is particularly associated with seagrass beds, at depths of roughly 2 to 15 metres (6–49 feet). Its camouflage and slow, deliberate movements help it avoid predators among the weed and rubble.

In the aquarium it appreciates live rock and some sheltered areas, ideally in a mature system where it can forage naturally.

Care Requirements

Keep it in 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 only about 12 cm (4.7 inches), it can be kept in tanks of around 75 litres (20 US gallons) or more. It is a slow, peaceful fish that should not be housed with aggressive or fast tankmates that will outcompete it.

A mature tank with natural microfauna helps support it between feedings, and of course a population of Aiptasia gives it an immediate purpose.

Diet & Feeding

This filefish is an omnivore that feeds on small invertebrates — amphipods, polychaete worms and molluscs — as well as Aiptasia anemones, which it readily consumes in the aquarium. Because it cannot live on Aiptasia alone, supplement its diet with frozen mysis and brine shrimp, finely chopped seafood and quality marine preparations. Feed regularly, especially once it has cleared a tank of pests, to keep it from grazing on corals out of hunger.

Behavior & Temperament

The Aiptasia-eating Filefish is peaceful and rather shy, drifting slowly around the rockwork as it forages. It is generally kept singly. Its calm temperament makes it easy to bully, so choose tankmates carefully and give it a settled, low-stress environment.

Tank Mates

Suitable companions are peaceful reef fish — gobies, smaller wrasses, cardinalfish, clownfish and similar — that won't harass it. Avoid aggressive or boisterous species. With invertebrates, exercise caution: while it targets Aiptasia, it may also nip at coral polyps, clam mantles and ornamental shrimp, so it is best deployed in tanks with hardy corals or where pest control is the priority.

Breeding

Acreichthys tomentosus has been bred in captivity by dedicated hobbyists; pairs deposit eggs among algae or substrate. Rearing the young requires suitable small foods and is uncommon, so most trade specimens are wild-collected.

Common Health Issues

This filefish is reasonably hardy but, like all marine fish, can be affected by marine ich (Cryptocaryon irritans) and marine velvet (Amyloodinium ocellatum), particularly when stressed. As a slow feeder it is also prone to losing condition if outcompeted, so ensure it gets enough food. Quarantine new arrivals, keep water quality stable, and provide a calm tank — do that, and this characterful little fish will earn its keep against Aiptasia while remaining an interesting resident in its own right.