Aiptasia is the pest that punishes impatience. Almost every method that feels satisfying — scraping it, cutting it, pulling it off the rock — is the method that turns one anemone into fifteen. Understanding why explains the whole treatment approach.
Why it spreads when you attack it
Aiptasia reproduces asexually by pedal laceration: it leaves behind small pieces of its foot tissue, and each fragment can grow into a new anemone. When you scrape or tear one off the rock, the body comes away and the foot does not. You have not removed a pest, you have propagated it — and you have scattered fragments across the tank in the process.
This is also why a stressed aiptasia is a dangerous aiptasia. Damage it without killing it and it responds by reproducing.
What works
Injection. The standard approach is injecting the anemone with a paste or solution that kills it in place, so the foot dies with the body. The technique matters more than the product: get the tip into the oral disc, inject enough to visibly distend the animal, and turn your pumps off for a few minutes so nothing you release drifts to a new rock. Do a few at a time rather than a whole rock in one session — releasing a lot of dead tissue at once is a water quality event.
Biological control. Peppermint shrimp (Lysmata wurdemanni — identification matters, several look-alikes will not touch aiptasia) and berghia nudibranchs both eat it. Berghia are the specialists: they eat nothing else, which makes them extremely effective and also means they starve once the job is done. This is the low-effort path for an established infestation, and it reaches the anemones you cannot see, which is more than any injection can claim.
Removing the rock. If the infestation is on one loose piece, taking it out and dealing with it outside the tank is the cleanest solution available. Nothing you do in a bucket can spread to the display.
What does not work
Scraping. Cutting. Pulling. Lasering half of it. Boiling water syringed at it, which mostly cooks the coralline around it. Hoping a tang will take an interest. All of these either leave the foot behind or leave fragments in the water column.
The part that matters most
To be clear about one thing: no coral dip removes aiptasia, including ours. Coral dips target flatworms, nudibranchs, red bugs and similar hitchhikers. Aiptasia is an anemone, it is not affected by a dip, and any product claiming otherwise is not being straight with you. What prevents aiptasia is inspection.
Aiptasia arrives on frag plugs, live rock, snail shells and in shipping bags. It does not appear from nowhere. Inspect every incoming coral before it goes in — including the underside of the plug, not just the coral. If you find even one small aiptasia on a plug, do not put that plug in your tank. Mount the coral on a fresh plug and discard the old one. A quarantine period on new arrivals catches the rest.
The reefers who never have an aiptasia problem are not lucky. They just never let the first one in.
Know what you are looking at
Aiptasia gets confused with majano anemones and with several harmless hitchhikers, and the handling differs. Our Coral Pest ID & Treatment Guide is 29 pages of photographs and treatments covering aiptasia, majano, flatworms, nudibranchs, red bugs, vermetids and the rest — an instant PDF download you can have open on your phone while you are looking at the rock.
For the full inspection-and-dip routine that keeps every other hitchhiker out, see The Complete Coral Dipping Guide, or get everything in the Complete Reef Care Library.