Long Nose File Fish (Oxymonocanthus longirostris) - (No Online Purchases)

The Longnose Filefish (Oxymonacanthus longirostris), also commonly known as the Orange-spotted Filefish or Harlequin Filefish, is a fascinating marine species.

It is highly distinctive due to its vivid colouration and specialized diet, making it a challenging but rewarding fish for experienced saltwater aquarists.

Diet and Aquarium Care

The Longnose Filefish has a very specialized diet, which is the main reason it is considered difficult to keep in captivity.

Wild Diet: It feeds almost exclusively on the polyps of Acropora corals. Its specialised snout is evolved for this precise grazing.

Aquarium Diet Challenge: Wild-caught specimens are notoriously difficult to transition to prepared foods. They are grazers and need to feed frequently throughout the day.

Captive Feeding: For the best chance of survival, captive-bred specimens are strongly preferred as they are more likely to accept prepared foods.

Recommended Foods:Small, meaty frozen foods should be offered frequently (at least 3-5 times a day), such as : Finely chopped Mysis shrimp or clam meat Nutrient-enriched Brine shrimpFish eggs or rotifers (due to their small size) Some success has been reported with prepared foods like Masstick or high-quality small pellets.

Aquarium Setup:

Tank Size: A minimum of $400$ liters ($100$ gallons) is often recommended, especially for long-term care and grazing space.

Water Quality: Excellent and stable water quality is essential, with pristine parameters ($0$ ppm ammonia/nitrite, low nitrate).

Flow: They prefer low to moderate water flow, as they are not powerful swimmers.

Reef Compatibility:This fish is generally not considered reef-safe. While some aquarists report them not damaging certain corals (especially if well-fed), their natural diet means they will typically nip at and consume coral polyps, particularly those of SPS (Acropora is their favourite).

Health and Behaviour: They are generally peaceful but should only be kept with very passive tankmates (like seahorses or pipefish) so they do not have to compete for food. They often live in monogamous pairs.

Disease: They are sensitive to sudden changes in water parameters and can be susceptible to common marine ailments like Marine Ich (Cryptocaryon irritans) or Velvet (Oodinium ocellatum) if stressed. A proper quarantine process for new arrivals is highly recommended.