Butterflyfishes: Auriga (Threadfin butterflyfish,Chaetodon auriga), Raccoon (Chaetodon lunula), Klein’s (Chaetodon kleini), Long-Nosed (Genus Forcipiger species), Teardrop (Chaetodon unimaculatus), and Copperband (Chelmon rostratus).
Some of the larger marine Angelfishes will eat Aiptasia for sure. The Queen (Holacanthus ciliaris) and some of the Dwarfs of the genus Centropyge have been cited. .
Filefishes: There are four species of Genus Acreichthys filefishes, but the Bristle-Tail Filefish (Acreichthys tomentosus) from the Indo-Pacific region is said to be the ultimate choice aiptasia eater.
Puffers: The Guinea Fowl (Arothron meleagris) may eat aiptasia, but it grows to a very large size, therefore the Tobies, or Sharp-Nosed species of the Canthigastrinae sub-family might be more suitable.
Shrimps: The “true” Peppermint Shrimp (Lysmata wurdemanni) is by far the top choice of aquarists for eating aiptasia anemones, but the trick with this one is making sure you get the right species. Although the Camelback Shrimp(Rhynchocienetes uritai) is very often misrepresented and sold as a true Peppermint Shrimp, it is the L. wurdemanni species that usually preys on aiptasia anemones, whereas the R. uritai will most likely ignore them. Hingeback Shrimp or Dancing Shrimp Rhynchocinetes durbanensis as well as other Rhynchocinetidae sp. are some others to be careful with. These species will also eat Aiptasia anemones, but because they will definitely snack on corals, they are not at all suitable for a reef tank.
Hermit Crabs: Almost always reef safe, and benefical algae eaters as well, in particular one or two of the more common Red Legged Hermit Crab (Dardanus megistos) might do the trick.
Nudibranches: Berghia Sea Slugs are a popular choice, because they are 100% safe, and effective when used and cared for properly. These nudibranches solely eat aiptasia, and will die without them present, which means you have take steps to ensure their survival.
Chemically burning the Aiptasia both internally and externally through the localized underwater application of concentrated aqueous Sodium Hydroxide solution, NaOH. The advantage of this method is that it’s not necessary to actually inject the Aiptasia with the chemical — just get the end of the applicator tube as close as possible to the Aiptasia or its hole in the rocks, and squirt a little drop of the NaOH into the water above the target. The intense boiling “heat of dilution” of the concentrated solution as it enters the tank water, coupled with the chemical burning action of the highly basic solution, kills the entire Aiptasia quite handily.