Montipora-eating nudibranch (pest) (Phestilla subodiosa) care guide

Group
Other invertebrates
Other names
Montipora nudibranch, Montipora-eating nudibranch, Phestilla sp. (before 2020)
Family
Trinchesiidae
Origin
Western Pacific: records from Korea, Hong Kong and Thailand; spread through the aquarium trade on Montipora frags
Water
saltwater
Maximum size
1 cm
Reef safe
no

Care

The Montipora-eating nudibranch is a tiny sea slug, usually well under 1 cm, that eats Montipora corals. It was named as a species only in 2020; before that hobbyists simply called it the Montipora nudibranch or Phestilla sp. Adults are translucent, with finger-like cerata speckled with brown, so they blend perfectly with the coral tissue; juveniles have white pigment across the body. How it arrives: on Montipora colonies and frags, often as eggs or juveniles that are almost invisible. Plating Montipora (such as M. capricornis) are most often affected, but encrusting types are also eaten. Identifying it: look for patches of bare white skeleton spreading across a Montipora, especially from the underside or edges. Check the underside of plates with a torch: the slugs sit pressed against the coral, and the eggs are laid as small white spiral or coiled ribbons on the underside and on bare skeleton. Harm: a population can strip whole Montipora colonies. Because the slugs breed in the tank, numbers rise quickly once they are established. Removal and prevention: dip and quarantine all new Montipora. Coral dips (iodine or specialist pest dips) remove adults, but eggs survive, so repeat dips or inspection over several weeks are needed, and scrape away egg masses and bare skeleton. Some keepers cut off and discard badly affected parts. Some wrasses (for example six-line and melanurus wrasses) are reported to eat them, but they are not reliable. Remove Montipora from the tank for several weeks to starve them out if needed. 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 invertebrates. Never dose copper in a tank holding this animal, and check fertiliser and medicine labels before use. Sources: SeaLifeBase (sealifebase.se/summary/Phestilla-subodiosa.html). Checked October 2026.

Diet

Corallivore: eats the living tissue of Montipora corals.

Breeding

It breeds rapidly in the aquarium, laying white coiled egg masses on the coral. Because the eggs resist many dips, repeat treatment or inspection over the hatching period is needed to clear an outbreak.

Compatibility and tank mates

A pest in any reef with Montipora. Harmless to other animals, but it destroys Montipora colonies. Possible predators include some wrasses.

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

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