Bristletail File Fish

Common Name: Aiptasia Eating Filefish, Bristletail Filefish, Matted Filefish, Matted Leatherjacket.
Scientific Name: Acreichthys tomentosus.
Distinguishing Features: Colouration can vary and be almost any shade from a very pale green through a dark mottled brown. The pigment is distributed over the body in a camouflage pattern allowing them to effectively blend in with algae’s. They are reported to be able to colour/shade to blend in to their environment. They are thin with an elongated dorsal fin, much like a triggerfish. They grow to about 12 to 15 cm.
Distribution: Found throughout the Indopacific region to East Africa, as far north as Ryukyu Islands, and as south as New South Wales (Australia).
Natural Habitat: Bristletail (A. tomentosus) is a reef inhabitant where it hunts prey among the coral/rock formations. It is most frequently found on the reef edge and over areas of rubble in shallow water. Its markings help camouflage it in potentially algae covered environments.
Captive & Feeding Requirements: Having kept many of these fish, my number one food recommendation would be mysis shrimp. These evoke a strong feeding response from this fish. Once established I have seen them eat everything offered from small pellet to flake foods. Like all fish, variety is the key to success and I would recommend a healthy diet of small chopped meaty foods such as shrimp, krill, mysis, squid, etc. Take into account the small mouth size when preparing such foods. Easy to keep so long as the fish is eating at the time of purchase. Care should be taken when introducing to a heavily stocked aquarium as other fish may see this camouflaged filefish as a piece of algae, and try to nip it. Once they are acclimated, they seem to do very well.
This fish appear to be very non-aggressive and is actually somewhat shy in the marine aquarium. I have heard of aggression between other members of the same species, but have also successfully housed several specimens at once. However, I have not tried introducing a second specimen to a tank with an established adult.
Reef Tank Compatibility: Generally no issues with compatibility, however A. tomentosus will eat pods in the aquarium and may reduce the local population below that able to sustain a healthy Mandarin fish. Another fact the potential owner should be aware of is that there are several reports of these fish nipping on other things in the tank besides aptasia. I have seen rare occurrences of zoanthids, LPS, fan worms, yellow polyps and other small sessile invertebrates being nipped. While none of these seem to be a major food source, the filefish does appear to be an opportunistic feeder at times. This may be further compounded by several misidentified fish reaching the aquarium trade. Similar fish from Florida and the Caribbean have been misidentified as A. tomentosus and are more likely to nip corals. Of all the corals/invertebrates that A. tomentosus has been known to pick on, the one I have seen it predate multiple times are bristle worms. Without a doubt, these small fish will actively reduce the bristle worm population.
Summary: The Aiptasia eating filefish lives up to its name, but care should be exercised when introducing one to a tank heavily stocked with xenia, mushrooms, or polyps. While not all will nip at corals, some do.