Bristle-tail File-fish (Acreichthys tomentosus) M

Overview

The Bristle-tail File-fish (Acreichthys tomentosus) is a fascinating marine species prized by aquarists for its unusual shape, calm demeanour, and potential usefulness in reef systems. Sometimes called the Aiptasia-eating filefish, this species is often chosen by hobbyists looking for a distinctive fish that can help with nuisance anemones while adding character to the aquarium. The body is laterally compressed and leaf-like, with a textured appearance that helps it blend into its surroundings. Its small size and deliberate swimming style make it a standout addition to a well-established marine tank.

Although generally peaceful, the Bristle-tail File-fish is not a beginner fish in the strictest sense. It does best in a mature aquarium with stable water quality, plenty of live rock, and a varied diet. Individual behaviour can vary, especially when it comes to reef compatibility, so careful observation is always recommended. This species is best suited to aquarists who already have some marine experience and want a fish with both personality and practical value.

All fish are supplied with our live arrival guarantee and fast UK delivery, helping ensure your new arrival reaches you in the best possible condition.

Care at a Glance

Origin & Natural Habitat

Acreichthys tomentosus is found across the Indo-Pacific, including tropical coastal waters, lagoons, seagrass beds, and sheltered reef areas. In the wild, it tends to inhabit areas with plenty of cover such as branching corals, rubble zones, and areas of mixed algae and sponge growth. Its mottled, textured appearance is an excellent example of natural camouflage, allowing it to blend in with its environment and avoid predators.

This habitat preference is important in the aquarium. A tank with abundant rockwork, shaded areas, and natural grazing surfaces helps the fish feel secure and encourages more natural behaviour. Because it is a slow, methodical swimmer, it appreciates a layout that offers hiding places without excessive current in every part of the tank.

Tank Setup & Water Parameters

A mature marine aquarium of at least 200 litres is recommended for a single Bristle-tail File-fish. Larger systems are even better, especially if you plan to keep it with other peaceful marine fish. A well-established tank with stable salinity, low nitrate, and excellent filtration is essential. This species can be sensitive to poor water quality and sudden changes, so consistency matters more than chasing exact numbers.

Provide plenty of live rock for grazing, shelter, and exploration. A natural aquascape with caves, ledges, and open swimming lanes works well. Moderate flow is ideal; avoid strong, turbulent currents that may stress the fish or make feeding difficult. Good lighting is beneficial for reef systems, but the fish should always have shaded retreats available.

Recommended water parameters are 24–28°C, pH 8.1–8.4, and stable marine salinity around 1.023–1.025 specific gravity. As with all marine livestock, regular testing and routine maintenance are key. Keep nitrate as low as practical and ensure oxygenation is strong, particularly in warmer weather. Acclimation should be slow and careful, as this species can be shy when first introduced.

Feeding Guide

The Bristle-tail File-fish is an omnivore with a preference for small meaty foods. In the aquarium it should be offered a varied diet including enriched frozen mysis, chopped seafood, brine shrimp, and high-quality marine preparations. Some individuals will also accept pellets or flakes, especially once settled, but many do best when fed a mix of frozen and prepared foods.

One of the reasons this species is so popular is its reputation for eating Aiptasia anemones. While many specimens do consume them, this is not guaranteed and should not be relied upon as the sole reason for purchase. Even if it does help with nuisance anemones, it still needs a proper feeding regime to remain healthy. Offer small meals once or twice daily, and observe body condition to ensure it is eating well.

If keeping in a reef tank, remember that individual fish may occasionally nip at soft corals, zoanthids, or fleshy polyps. A well-fed fish is generally less likely to sample corals, but no file-fish can be considered completely risk-free in every reef setup.

Tank Mates / Compatibility

The Bristle-tail File-fish is best kept with peaceful to mildly assertive tank mates that will not outcompete it for food. Suitable companions include clownfish, gobies, blennies, cardinalfish, chromis, small wrasses, and other non-aggressive community marine species. It can also work well in fish-only systems with similarly sized, calm tank mates.

Avoid housing it with aggressive triggers, puffers, large predatory fish, or highly territorial species that may harass or intimidate it. Fast, boisterous feeders can also be a problem if the file-fish is shy or slow to adapt. In reef aquariums, caution is advised with delicate corals and ornamental invertebrates, as individual behaviour varies and some specimens may nip at soft-bodied livestock.

For best results, introduce the Bristle-tail File-fish to a mature, peaceful aquarium where it can settle without competition. Feeding at the same time each day and ensuring it has plenty of cover will help it thrive.

Why Buy from Tropical Fish Co

At Tropical Fish Co, we focus on supplying healthy marine livestock with careful handling from our systems to your door. Your Bristle-tail File-fish is packed with attention to welfare and dispatched using fast UK delivery, helping reduce transit stress and improve the chances of a smooth acclimation. We also offer a live arrival guarantee for added peace of mind.

We understand that marine fish need more than just a box and a label. That is why we aim to provide accurate care information, reliable service, and support for aquarists at every stage. Whether you are adding a single standout specimen or building a carefully planned marine community, we are here to help you choose the right fish and keep it thriving.

Choose Tropical Fish Co for quality livestock, dependable delivery, and practical advice you can trust.