Filefish: ID, Toxic Species, Taste and Reef Tank Care

A filefish is a flat, diamond-shaped reef fish in the family Monacanthidae, a close relative of triggerfish and pufferfish. Wikipedia counts about 102 species in 27 genera, found in shallow tropical and subtropical water in the Atlantic, Pacific and Indian Oceans, usually shallower than 30 metres around reefs, seagrass and floating Sargassum. More than half of all species, 58 in 23 genera, live in Australian waters. Filefish are also called leatherjackets (Wikipedia).

Filefish swim poorly with small fins and often hang head-down among seaweed, changing colour quickly to match their background (Wikipedia).

The name comes from the skin. Filefish have rough scales that do not overlap and carry tiny spikes, so the skin feels like a woodworker's file or sandpaper (Wikipedia).

The other feature to look for is a single long spine on top of the head. It can be raised and lowered; a much smaller second spine behind it only locks the first one upright (Wikipedia). Triggerfish lock their spine in a similar way, which is one reason the two groups are confused.

Both belong to the order Tetraodontiformes and both have a locking dorsal spine. Things you can check in a photo:

• Dorsal spine: a filefish shows one tall, retractable spine; the second spine is much smaller and only locks the first (Wikipedia)
• Body: filefish are very thin from side to side and look diamond-shaped; they drift and tilt rather than swim hard (Wikipedia)
• Skin: rough, file-like skin made of small, non-overlapping spiky scales (Wikipedia)

For the triggerfish side, see our triggerfish page. FishLens suggests a name from one photo. Photograph the fish side-on with the dorsal spine visible.

Some are, and the best-known case is the scrawled filefish, Aluterus scriptus. Wikipedia states that it contains palytoxin, which it describes as 50 times more toxic than tetrodotoxin; its diet includes colonial anemones (Florida Museum). FishBase and the Florida Museum both record reports of ciguatera poisoning from this species as well.

How to recognise a scrawled filefish (Florida Museum):

• Olive-brown to grey body covered with irregular blue spots and short blue lines plus small black spots
• A long, rounded, ragged-edged tail, which gives it the name broomtail filefish
• Large: commonly 55 cm and up to 110 cm

If you catch one, release it. If anyone becomes unwell after eating any reef fish, especially with tingling lips, numbness, weakness or breathing trouble, call your local emergency number or Poison Control (1-800-222-1222 in the US) straight away.

Some filefish are fished and eaten on a large scale, but that does not make every filefish safe. Wikipedia reports a commercial catch of roughly 200,000 tonnes a year, mostly Cantherhines species; in Korea the threadsail filefish is dried and sold as a snack called jwipo, and in Japan filefish liver is treated as a high-end ingredient.

On taste, the fishing site SaltwaterMecca describes the meat as firm and sweet, closer to crab or lobster than to fish, and says the rough skin is removed before cooking. We have not tasted it and cannot confirm that.

Before eating any filefish:

• Confirm the species; do not eat the scrawled filefish (see above)
• Check local advice on ciguatera. Clemson University's Home and Garden Information Center notes that ciguatoxin is not destroyed by cooking or freezing and that a toxic fish looks, smells and tastes normal
• Follow your state's size and bag rules

If anyone feels ill after eating reef fish, contact a doctor or Poison Control.

Aquarists buy one species above all: the aiptasia-eating filefish, Acreichthys tomentosus, which eats the pest anemone Aiptasia. The Biota Group, which sells captive-bred fish, gives these care notes:

• Grows to about 3.5 inches; minimum tank 30 gallons
• 72 to 78F, pH 8.1 to 8.4
• Eats most aquarium foods, including frozen and pellet foods
• Reef safe with caution: it may nip soft corals, zoanthids, SPS polyps, fleshy LPS, clam mantles and ornamental shrimp
• Poor swimmer, so cover pump intakes and keep flow moderate

Avoid the orange spotted filefish, Oxymonacanthus longirostris, unless you can supply live Acropora coral: Wikipedia describes it as an obligate coral-eater of which few survive long in captivity, and it is listed as Vulnerable.

Prices checked on 2026-09-25: LiveAquaria listed the aiptasia-eating filefish at $41.99 to $59.99, the tassle filefish from $49.99, the honeycomb filefish at $79.99 and the clown filefish from $189.99; The Biota Group listed captive-bred aiptasia-eating filefish at $50 to $70.

One detail most filefish pages leave out: the orange spotted filefish takes on chemicals from the Acropora coral it eats, and this masks its scent from predators such as cod. Wikipedia notes this kind of smell camouflage has not been observed in other vertebrates. It is also why the species depends so heavily on healthy branching coral, and why coral bleaching is its main threat.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices and rules are given with the date we checked them; they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.