Scientific Name: Acreichthys tomentosus

Identification: A small, laterally compressed filefish with a mottled tan, brown, and green pattern that mimics seagrass and algae. Skin has a rough, velvety texture. A single dorsal spine sits above the eye. Coloration can shift slightly to blend with surroundings.

Maximum Length: 4 inches (10 cm)

Origin: Indo-Pacific — found from the Red Sea and East Africa east to the Marshall Islands, north to southern Japan, and south to Australia.

Minimum Tank Size: 30 gallons

Behavior: Generally peaceful toward other fish. May be kept singly or as a mated pair. Known for its unique ability to eat aiptasia (glass anemones), making it a popular biological control for reef aquariums plagued by aiptasia outbreaks. May also consume other small anemones and soft-bodied invertebrates.

Feeding and Diet: The primary draw of this fish is its appetite for aiptasia anemones. In the aquarium it will also accept Mysis shrimp, finely chopped seafood, frozen preparations, and small pellet foods. A varied diet helps maintain health once the aiptasia supply runs out. Feed 2–3 times daily.

Reef Compatibility: Use with caution. This fish is excellent for eliminating aiptasia but may also nip at small-polyp stony corals (SPS), zoanthids, or other sessile invertebrates — especially after exhausting the aiptasia population. Monitor closely in mixed reef systems. Generally safer in FOWLR or LPS-dominated tanks.

Cautions: Once aiptasia is eliminated from the tank, supplement diet immediately to prevent the fish from turning to corals or other invertebrates. Not recommended with ornamental shrimp or other small invertebrates it may target. Best kept with peaceful tank mates of similar size.