Coral pests can arrive on any new frag or rock. They often hide in plain sight. Fast action can save a whole reef.
This guide covers the most common coral pests. You will learn what to look for. You will also learn how to remove them safely.
How pests get in and what to inspect first
Most pests enter on new coral bases, plugs, and rubble. Eggs can survive shipping and short dips. A clean-looking frag can still carry a problem.
Start with a strong visual check. Use white light and a magnifier. Look under the frag, around the glue, and between polyps.
Inspect at night, too. Many pests feed after lights out. Use a flashlight with a red lens to reduce coral stress.
Set up a simple quarantine tank for new corals. A 5 to 10 gallon tank works well. Match salinity at 1.025 and temperature at 78°F. Keep alkalinity stable near 8 to 9 dKH.
- Check for bite marks, missing tissue, and pale patches.
- Look for egg spirals, jelly-like clumps, and tiny moving dots.
- Blow the coral with a turkey baster and watch what falls off.
Keep a log of arrivals and dips. Note dates and results. This helps you spot patterns over time. For a full intake routine, see our coral quarantine checklist.
Top coral pests and clear warning signs
Acropora-eating flatworms target SPS. You may see faded tips and patchy polyp extension. Eggs often appear as tiny tan clusters on the base. A baster blast can reveal flat, oval worms.
Montipora-eating nudibranchs hit montis hard. They leave clean white bite trails. Adults look like tiny white slugs. Eggs form tight white coils on shaded edges.
Red bugs irritate Acropora polyps. They are tiny orange specks on smooth skin. Corals may brown out and stop growing. A macro photo can confirm them.
Zoanthid pests include sundial snails, spiders, and nudibranchs. Polyps may stay closed for days. You may see a cone-shaped snail near the skirt. Some spiders hide under the mat.
- Flatworms: tissue thinning, dull color, eggs on the base.
- Nudibranchs: bite tracks, missing edges, egg spirals.
- Red bugs: poor polyp extension, slowed growth, tiny orange dots.
Also watch for vermetid snails and aiptasia on plugs. Vermetids cast mucus webs that irritate nearby tissue. Aiptasia can sting and spread fast. For ID help, use our reef pest identification guide.
Dips, manual removal, and a simple treatment plan
Dips remove many mobile pests, not most eggs. Use a dedicated container and match temperature and salinity. Typical dip times run 5 to 15 minutes. Always follow the product label.
After the dip, rinse in clean saltwater. Then inspect again under bright light. Use tweezers to pull off nudibranchs and snails. Scrape egg coils from the base with a pick.
Plan for repeated treatments. Many eggs hatch in 4 to 10 days. Dip every 4 to 7 days for 3 to 4 rounds. Keep the coral in quarantine for at least 21 to 30 days.
Common mistakes cause reinfestations. Do not dip in the display tank. Do not reuse dip water. Do not trust “pest free” labels. If a colony shows rapid tissue loss, isolate it at once.
- Use a baster daily in quarantine to dislodge hidden pests.
- Remove frag plugs when possible and remount on clean discs.
- Keep nutrients steady to reduce stress during treatment.
If you see pests in the display, act quickly. Remove the coral and treat in a separate container. Then inspect nearby frags and rock. For stability tips during recovery, read stable reef water parameters.
Sources: Borneman, E. “Aquarium Corals”; Delbeek & Sprung, “The Reef Aquarium” Vol. 1-3; Julian Sprung, “Corals: A Quick Reference Guide”.
By
