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Choosing a Filefish

The filefish, Oxymonocanthus longirostris, is one of the most striking saltwater specimens. It belongs to a family of fish known as Balistidea and is a relative of the Triggerfish. Like its cousin, the filefish has the ability to raise its spinous dorsal fin and lock it into place. This raised spine makes it difficult for the filefish to be consumed by predators. These shy fish are natives of the Indo-Pacific and are quiet grazers. Hobbyists often find it difficult to adapt them to captive feeding.

Appearance and Behavior

Filefish look as though they have been assembled by a committee, and everyone had a different thought in mind. They have an elongated orange snout, which blends into an aquamarine colored body. The entire length of the body is covered with bright orange spots. The orbit of the eye is rimmed with an alternating green and orange pattern. Their scales are very rough in texture, earning them the nickname of “leatherjackets.”

Filefish are peaceful grazers, feeding on algae and coral polyps. It is this particular food preference that makes it difficult for filefish to adapt to aquarium conditions. They often need to be isolated and hand fed to coax them into accepting new foods. If put in a tank with live corals, there may be losses as the filefish consume the polyps.

Feeding and Tank Requirements

Tempting your filefish to eat will be challenging. Filefish are considered difficult feeders and often times do not make the transition to prepared foods. You may have to do a little creative cooking for them. When you buy your fish, ask your supplier what they have fed with success. Recently obtained fish should probably be watched for a week or so until you’re sure it’s eating before making a final purchase. Try offering small bits of fish, shellfish or beef heart initially. They will graze these small pieces of food from the bottom of they tank. A leaf of romaine, endive or leaf lettuce can be offered. Blanch the lettuce to make it a bit more tender.

Special Concerns

Filefish are not active swimmers. They will need cover to protect them from larger more aggressive fish. Try a few rocky outcroppings or coral formations to make them feel more at home. You may want to consider keeping them alone or in a species tank.