Acropora-eating flatworm (AEFW) (Prosthiostomum acroporae) care guide

Group
Other invertebrates
Other names
AEFW, Acropora-eating flatworm, Acro-eating flatworm
Family
Prosthiostomidae
Origin
Indo-Pacific reefs; spread worldwide on aquarium Acropora
Water
saltwater
Reef safe
no

Care

The Acropora-eating flatworm (AEFW) is a small, flat polyclad flatworm that feeds only on the tissue of Acropora corals. It is a serious reef-tank pest. Our sources have little on this species; the figures are general guidance, not from a source. How it arrives: on Acropora colonies and frags, as adult worms or as egg clusters stuck to bare skeleton at the base of a frag or on its plug. Identifying it: adults are oval and only a few millimetres long, with a translucent brown body that matches the colour of the coral, so they are hard to see. Signs are round bite marks or patches of missing tissue, a coral that looks pale or blotchy, and clusters of tiny brown or gold egg capsules on dead skeleton. Shining a torch or blowing a jet of water over the coral, or a coral dip, will often show worms. Harm: they eat Acropora tissue, and a heavy infestation can kill colonies and spread to every Acropora in the tank. Removal and prevention: dip every new Acropora in a commercial coral dip made for flatworms, then inspect it and remove any egg clusters by hand or by cutting off bare skeleton. Eggs survive dips, so repeat dips over several weeks to catch worms as they hatch, ideally with the coral kept in a quarantine tank for several weeks. In the display, remove and dip affected colonies. Some wrasses (for example six-line and melanurus wrasses) eat flatworms but will not cure an outbreak. Not livestock: this is a pest and should not be sold as livestock. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never dose them in a tank holding this animal, and read the label of any treatment, fertiliser or algae remover before use. Sources: none available for this species; general hobby knowledge. Checked October 2026.

Diet

Acropora coral tissue only.

Breeding

Lays clusters of eggs on bare Acropora skeleton. They hatch after a few weeks, which is why repeated dips and quarantine are needed.

Compatibility and tank mates

Not reef safe: it kills Acropora. Other corals are not affected. Some wrasses pick at flatworms.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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