Acreichthys tomentosus, commonly known as the bristle-tail filefish or Aiptasia-eating filefish, is a species of demersal marine fish which belongs to the family Monacanthidae and is widespread throughout the tropical waters of the Indo-west Pacific.

It is a small fish that can reach a maximum size of 12 cm (4.7 in) length and has the ability to rapidly change color and skin texture and patterns as to avoid detection and consequently predation.

[3] It is found in the waters around Sri Lanka, Ishigaki island, the Philippines, Indonesia, New Guinea, Queensland, New Caledonia, and Tonga.

It prefers temperatures of 27.6–29 °C (81.7–84.2 °F), a dissolved oxygen concentration of 4.51-4.59 mL/L (4510-4590 ppm), and a depth of 2–15 m (6.6–49.2 ft).

[1] It is commonly kept in aquaria as a member of the clean-up crew for its willingness to eat Aiptasia anemones, a common aquarium pest.