Coral Pests: How to Spot Them Before They Spread
Most reef pests arrive as hitchhikers on new corals or rock. Catching them early, before they spread, saves a lot of time and corals. Here are the most common pests and how to keep them out.
Common coral pests
| Pest | What it looks like | What it affects |
|---|---|---|
| Zoa-eating nudibranchs | Small slugs camouflaged to match the polyps | Zoanthids and palythoa |
| Montipora-eating nudibranchs | Tiny white to tan slugs, egg spirals under plates | Montipora |
| Euphyllia-eating flatworms | Small flat worms on the tissue | Hammers, torches, frogspawn |
| Acropora-eating flatworms | Tan flatworms, bite marks, egg clusters on the skeleton | Acropora |
| Red bugs | Tiny red or yellow specks on the branches | Acropora |
| Sea spiders | Thin-legged, spider-like pests between polyps | Zoanthids and soft corals |
| Aiptasia | Small brown pest anemones that spread fast | Sting nearby corals |
How to spot pests
- Check corals with a flashlight after the lights go out, when many pests are active.
- Look for bite marks, pale patches of missing tissue, or corals that stay closed.
- Inspect the underside of frag plugs and plates, where eggs often hide.
- A clip-on coral lens helps you see small pests clearly.
Prevention: dip and inspect
Dipping every new coral before it goes in your tank removes most pests. Dips usually don't kill eggs, so scrape off any egg clusters and consider a second dip a few days later. Follow our Coral Acclimation & Dipping Guide and shop our coral dips.
Quarantine
A separate quarantine tank, where new corals sit for several weeks before going into your display, is the most reliable way to keep pests out. It gives any eggs time to hatch so you can treat them before they reach your main tank.
If pests are already in your tank
Remove affected corals, dip them, and remove eggs by hand. Repeat dips until no pests appear in the dip water. For a tank-wide outbreak, research treatment options specific to that pest before acting.
Not sure what you're seeing? Send us clear photos and we'll take a look.