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Sooner or later, most reef tanks get an unwanted hitchhiker. Some are harmless or even helpful. Others, like aiptasia, can spread across your rockwork and sting your corals if you don't act. The sooner you identify a pest and deal with it, the easier it is to control.
Aiptasia (glass anemones)
How to identify it
Aiptasia are small, brown or translucent anemones with long, thin tentacles, usually 1–5cm across. They grow in crevices and on the backs of rocks, retract into holes when disturbed, and multiply quickly. They sting nearby corals and compete for space.
Why they spread
Aiptasia reproduce by splitting and by leaving tiny pieces behind when they're damaged. That's why scraping or pulling them off usually makes things worse: each fragment can grow into a new anemone. Excess nutrients from overfeeding help them grow faster.
How to get rid of aiptasia
- Treat each anemone directly. Turn off the pumps so the treatment doesn't drift. Apply a targeted aiptasia treatment close to the oral disc using the supplied syringe, approaching slowly so the anemone doesn't retract. Popular options include Blue Life Aiptasia RX, Maxspect Aiptasia Control, Joe's Juice and F-Aiptasia Reef Safe Aiptasia Fix.
- Repeat as needed. Large or hidden aiptasia often need a second treatment. Check the rock again a week later for any regrowth.
- Consider a biological control for widespread infestations. Peppermint shrimp and berghia nudibranchs eat aiptasia, although results vary between individuals. Berghia only eat aiptasia, so they need enough to survive.
- Reduce nutrients. Feed carefully and keep up with water changes so aiptasia have less to grow on.
See all aiptasia treatments.
Majano anemones
Majanos look like small green or brown anemones with short, bubble-tipped tentacles. They're just as invasive as aiptasia and can be treated the same way; Joe's Juice is formulated for both.
Flatworms
Red planaria (Convolutriloba) are small rust-red, oval flatworms that collect on rock, sand and coral in visible colonies. In large numbers they block light from corals, and when they die en masse they can release toxins.
- Siphon out as many as you can before treating, to reduce the toxic load.
- Treat the tank with a flatworm treatment such as Blue Life Flatworm RX or Korallen Zucht Flatworm Stop, following the instructions closely.
- Be ready for a water change and fresh carbon straight after treatment, as the label advises, to remove toxins released by dying worms. See our carbon media.
Acropora-eating flatworms (AEFW) and montipora-eating nudibranchs are harder to spot and are best prevented by dipping corals (see below).
Bristleworms
Most bristleworms are harmless scavengers that help clean up uneaten food. Small numbers are a sign of a healthy tank. A sudden population explosion usually means too much food. Feed less, and remove some with a pest trap such as the Aqua Medic Trap-Pest. Only large fireworms or very large bristleworms that are seen attacking corals or clams need removing urgently. Wear gloves when handling them; the bristles irritate skin.
Pest snails and other hitchhikers
- Vermetid snails live in tubes cemented to rock and cast mucus nets that irritate corals. Cover or glue over the tube opening.
- Pyramid snails are tiny, white snails that feed on clams. Remove them by hand or with natural predators such as wrasse.
- Mantis shrimp and crabs sometimes arrive in live rock. A loud clicking at night, or fish and snails going missing, are clues. A baited trap such as the Hobby Genius Fish Trap can help catch them. See our fish and pest traps.
Nuisance algae and cyanobacteria
Algae and cyanobacteria aren't true pests, but they're the most common thing reef keepers want rid of. Our guides on getting rid of algae in a reef aquarium and controlling cyanobacteria explain what to do.
Preventing pests in the first place
Dip every coral
Most pests arrive on new corals, frag plugs and rock. A coral dip removes many hitchhikers and their eggs before they reach your display. Dip new corals in a dedicated product such as Red Sea DipX, Coral Rx Pro or Seachem Reef Dip, following the label. Inspect the coral and plug closely afterwards, and remove any eggs on the base. Browse treatments and dips.
Inspect and quarantine
- Check new corals and rock under a torch before adding them.
- Remove frags from their plug where possible, or scrape the plug clean.
- Quarantine new corals in a separate tank for a few weeks if you can, especially Acropora and Montipora.
Start with clean rock
Dry, aquacultured rock carries no hitchhikers at all. If you're setting up a new reef, it's the simplest way to start pest-free. See our marine rock range.
If you're not sure what you've found, send our team a clear photo and we'll help you identify it before you treat.
