Aiptasia (glass anemones)

Identification

Translucent light-brown to tan polyps, often with faint longitudinal striping on the column. Body up to about 5 cm tall with an oral disc up to about 2 cm across ringed by many (up to roughly 100) long, slender tentacles tapering to sharp points. Pale or nearly clear in low light. They retract fast into rock crevices when disturbed and show up on live rock, frag plugs, clam shells, overflows and in sumps.

Often confused with

Majano anemones — majanos are shorter and stockier with stubby tentacles that end in rounded or bulbous tips, while aiptasia tentacles stay thin and pointed. Also confused with harmless curlycue or rock flower anemones, which are larger, more colorful and do not clone into plague numbers.

What it targets

No fixed host. They settle anywhere and sting corals within tentacle reach, irritating or killing LPS, SPS, zoanthids and clam mantles, and they compete for light and space.

How it spreads

Classic hitchhiker on live rock, coral bases, frag plugs and macroalgae. Inside a tank they spread by pedal laceration (tiny pieces of the foot left behind grow into new polyps), by budding and by planula larvae, so torn or partially killed polyps seed new ones.

Control (safest first)

Manual removal done completely: lift the whole polyp off with its foot using a scalpel or dental tool on removable rock, or seal the polyp and its hole over with reef epoxy or superglue. Never tear or scrub aiptasia in the tank — leftover foot tissue regrows into new polyps, so partial removal makes the problem bigger. Predators (see predators list): Berghia nudibranchs eat only aiptasia and work through rockwork you cannot reach; keepers report they need weeks to months and a group large enough to breed before numbers visibly fall. Peppermint shrimp (true Lysmata wurdemanni) eat small polyps but individual shrimp vary and some ignore aiptasia entirely. Spot chemical treatment: cover the oral disc with a thick kalkwasser (calcium hydroxide) paste or a commercial aiptasia product with pumps off so the paste stays put. Effective on polyps you can reach and fully cover; missed or upside-down polyps survive. Work in small batches per day — kalk paste raises pH and alkalinity, and drifting paste burns corals. Injection of lemon juice or near-boiling RO water into the disc: cheap and often effective on single polyps, but inconsistent, and a flinching polyp that retracts into rock usually survives it. Majano Wand (electrolysis wand): zaps individual visible polyps with no chemicals; useful for spot work, slow for heavy infestations and it cannot reach polyps deep in rockwork. Fish predators such as copperband butterflyfish, aiptasia-eating filefish and Klein's butterflyfish: can clear visible aiptasia in larger systems, but all may also nip corals, clams and other anemones — treat as not fully reef-safe before adding one.

Natural predators

• Berghia nudibranch→
• Peppermint shrimp→
• Copperband butterflyfish→
• Aiptasia-eating filefish / matted filefish
• Klein's butterflyfish

Field notes

A Reef2Reef keeper who ran Berghia twice in a wrasse tank advised adding them at night near (not on) aiptasia, warned that peppermint shrimp will eat Berghia that have fed and turned brown, and cautioned against stacking chemical treatments on top of Berghia because kalk paste and bottled aiptasia products can kill the nudibranchs too. Reports split on peppermint shrimp: one keeper cleared aiptasia that arrived on Florida live rock after adding roughly 30 peppermints with no coral losses, while another keeper on the same forum called shrimp a coin flip and warned they may move on to acans and other LPS once aiptasia runs out. Berghia timelines divide opinion as well — several keepers saw little change for the first weeks and then a collapse of the aiptasia population once the nudibranchs started breeding, with one estimating four to six months before results became obvious and a minimum group of about ten medium, egg-laying animals for a hunting pack.