Named after the terrestrial flower, Anemone, because of their often beautiful coloration and flower-like appearance, sea anemones are predatory animals that can be a wonderful but also risky addition to an aquarium. Notoriously difficult to keep, sea anemones, which we will hereafter refer to simply as anemones, often have very specific needs that can influence your entire aquarium ecosystem if you want to keep them thriving.


Sea anemones belong to the phylum, Cnidaria, class, Anthozoa, subclass, Hexacorallia and are related to Corals, Jellyfish and Hydra. The typical body structure of an anemone involves a columnar trunk topped by an oral disk with a ring of tentacles and a central mouth. The gastrovascular cavity serves as both a mouth and an anus with food coming in and waste and undigested matter going out.

A beautiful H. magnifica anemone.

Photo is from the Reef2Reef archives courtesy of @Birdy55 ©2019, All Rights Reserved.

Due to the column being composed of multiple sheets of muscle anemones have a remarkable ability to change shape and can lengthen or contract in any direction. They’re even capable of retracting their tentacles and oral disc or causing their gullet and mesenteries to turn inside out.


Anemones are also well known for their cnidocytes, or stinging cells, which they use to paralyze prey and draw it into their gaping maw. Most sea anemones don’t represent an immediate danger to humans, however, some species such as Actinodendron arboreum, Phyllodiscus semoni and Stichodactyla have caused severe injuries.

Regardless of anemone species, gloves are recommended when you are required to handle them. The toxins injected by the stinging cells are highly toxic to most fish and crustaceans but there are, of course, exceptions.

As one might guess from our previous information, they are primarily predatory though many have mistakenly thought they were photosynthetic. This isn’t an entirely false assumption as they do frequently have a symbiotic relationship with several species of single celled organisms like zooxanthellae, single-celled dinoflagellates and zoochlorellae that live within their cells. These organisms can produce oxygen and glucose through photosynthesis and pass it on to the anemone, which is quite beneficial for the animal.

A bubble-tip anemone.

Photo is from the Reef2Reef archives courtesy of @James M ©2019, All Rights Reserved.

These single-celled organisms are also responsible for the vibrant colors of many anemones, and their presence can be an indicator of the anemone’s health. Anemones are capable of both sexual and asexual reproduction, releasing sperm and eggs into the water for fertilization or undergoing a variety of splitting or fragging that leads to the growth of a new individual.

One of the reasons aquarists are fond of anemones as they and their attendant fish can make for attractive and charming displays. While anemones are predatory and have been known to feed on small crabs and fish there are several species of fish and invertebrates which can live well with anemones.

The most well known of these is, of course, the beautiful clownfish but cardinalfish, threespot dascyllus, incognito goby, opossum shrimp and several species of crab are also known to dwell on or with anemones.

A Colorado Sunburst bubble-tip anemone.

Photo is from the Reef2Reef archives courtesy of @FarmerTy ©2019, All Rights Reserved.

Be wary as symbiotic species may not always acclimate to the anemone you intend them to live in. If there is difficulty in the acclimatization process the anemone might end up making a meal of your fish, especially when they are juveniles.

There are also interesting examples of mutualism between anemones and other animals. A particularly fun example of this behaviour is the Pom Pom Crab, which has two little anemones attached to its claws that help it hunt.

It is also important to note that introducing anemones into tanks that already contain corals and other sessile invertebrates can be problematic as they may employ a form of chemical warfare against each other, emitting nasty excretions designed to clear the area of competitors. One frequently recommended solution for this chemical warfare is using activated carbon as it may help clear the water of any chemical weapons used by your invertebrates.

As well it is important to note that larger fish not directly threatened by the anemone will often “peck” at it’s tentacles and can injure the animal. Critters that are specifically bad for this are butterfly fish, large angelfish, triggers and large puffers. It is extremely important to be aware of how your specific anemones and their tank mates will react to each other as these poor choices can be detrimental to both the anemone and the other creatures.

Maintaining proper tank conditions for anemones is one of the most important elements of keeping them healthy and improper conditions is one of the most common reasons why anemones die in captivity, and why they have such a reputation for difficulty. Anemones are most likely to flourish in a tank that has matured and isn’t prone to big swings in water parameters. Anemones are particularly vulnerable to changes in the water, and as such, they are best kept in a very stable environment. They also do best with very high water quality as well as with some degree of good water flow. In fact, it is speculated that proper water flow is one of the most important factors in ensuring the long term survivability of your anemones.

They also have been known to like a high degree of dissolved oxygen in the water. As most anemones are somewhat mobile it’s important to ensure that your tank setup won’t harm them. To ensure that roaming anemones aren’t sucked in by your equipment, your intakes should all be screened, especially the intakes of pumps and powerheads. You should be careful not to remove an anemone from the tank during acclimatization as any water you transport it in is likely to be ammonia rich, which is bad for the animal.

When positioning an anemone in your tank you should choose an area with plenty of room, but also don’t be surprised if your anemone decides to move itself to a more desired location, as this is not unheard of.

Substrate requirements differ depending on anemone species so you should be careful to research the specific requirements for the specific anemone you want to place in your tank as some like fine silty sand and others like to attach themselves to harder surfaces. Actinodendron species, for example, require a layer of sand 6 inches deep.

In order to keep them from eating their tank mates and to ensure they won’t perish from lack of light it’s also important to consider supplemental feeding. Recommended foods are chopped meaty foods, pulverized flake foods. It’s important to avoid overfeeding as it could pollute the tank--once or twice a week is the recommended frequency. Keep an eye out as some anemones have been known to eject pellets of partially digested food, which can be a problematic source of pollutants.

Here are some factors to keep in mind when purchasing an anemone. Even though most anemones have stunning natural shapes and colorations some sketchier sellers have been known to dye anemones for sale, which is extremely bad for the animal and dooms them to an early death. Also keep in mind that paleness or a lack of any color in an anemone is a sign of poor health.

The most important place to inspect on an anemone you’re thinking of purchasing is the base or foot, as that is where all of the creature's internal organs are stored. A damaged base implies a poor collection of the animal and that it is unlikely to survive for long. Anemones should appear plump and full, ones that are shrivelled and covered in mucus are likely to be unhealthy. Ensure that you are using reputable sellers that engage in sustainable harvesting methods.

So now that we’ve covered the important basics of anemone keeping, what anemones are the best choices for your aquarium?

A large and healthy carpet anemone.

Photo is from the Reef2Reef archives courtesy of @RussiReef ©2019, All Rights Reserved.


Well here is a small curated list of some recommendations:

The Sebae Anemone, scientific name Heteractis crispa, has long thin tentacles with a pink dot at the center of each. It is an Indo-West Pacific Anemone that many species of clown fish will associate with.

The Malu Anemone, Heteractis malu, is a species with highly variable coloration and a long “stalk” that it buries in the substrate. It is another great clownfish anemone. The Condylactis gigantea or Giant Caribbean Anemone prefers a rocky substrate and has a symbiotic relationship with many species of crabs and shrimp. This anemone is quite demanding in terms of lighting.

The Bubble-Tip Anemone, Entacmaea quadricolor, is a hardy and inexpensive anemone that serves as an excellent host organism for clownfish, porcelain crabs and Periclimenes shrimp. Most species exhibit the bulb-tipped tentacles from which the anemone derives its name, but it is not uncommon for the bulbs not to occur, and this is not a problem. Fairly undemanding in terms of light and available in a massive variety of color morphs it makes an excellent starter anemone.

The Bartholomea annulta, Curlycue or Corkscrew Anemone are characterized by their namesake, curly-looking tentacles. Inexpensive and brightly colored, this is one of the less demanding anemones in terms of lighting. However, this species can be quite aggressive towards other invertebrates in the same tank. There is also another species known as The Corkscrew Anemone, the Macrodactyla doreensis. This anemone is dull orange or red in color and known to be hardy in the right environment.

Cerianthys Tube Anemones aren’t true anemones but have many of the same characteristics and are often labelled as anemones when sold. They are desirable for their fine tentacles and occasional bioluminescence. They famously construct a tube of specializes cells and like to bury themselves in deep, fine, silty substrate. A word of caution as they tend to snap up small fish that come by and are not symbiotic with any species of fish, crabs or shrimp.

As there are some excellent anemone species to keep in captivity there are also some that should be avoided or chosen with distinct caution.

Macrodactyla doreensis, a long-tentacle anemone, sometimes called a corkscrew anemone.

Photo is from the Reef2Reef archives courtesy of @Christopher Tracy ©2019, All Rights Reserved.


The Adhesive Anemone, or Cryptodendrum adhaesivum, can be unique in appearance and is often referred to as the Pizza Anemone however it has a potent sting that can be quite dangerous to other tank inhabitants.

The Giant Carpet Anemone, Stichodactyla gigantea, can play host to clownfish, threespot domino damsels and Periclimenes shrimp but have been occasionally known to eat their residents and can consume other fish and invertebrates with wild abandon. The giant carpet isn’t a complete no but it requires careful planning, stocking your tank with known symbiotic organisms, and being aware of the risks.

The Heteractis magnifica, or Ritteri Anemone, is not typically suitable for captivity despite being a good symbiont. It prefers rocky substrate and is quite mobile but is known to be very demanding, requiring several hundred litres as it can reach a size of 1 meter/3.3 feet. It also requites exceptional water quality, intense lighting and lots of water movement.

The Hell's Fire Anemone, Actinodendron arboretum, can frequently be found for sale and looks a bit like an underwater broccoli. However, while most sea anemones can have painful but ultimately harmless stings, the Hell’s Fire sting is highly venomous, and its stings can cause extremely painful skin ulcers.


We hope that we’ve armed you with enough knowledge to ensure the proper choice and successful care of these interesting, though temperamental, critters. As is frequently the case with marine livestock, anemones often arrive to fish stores in poor health or incorrectly labeled. So, do your homework, and if you are inexperienced, take a more experienced reefer with you to choose an anemone and, above all, buy from reliable sources.

Note from the Editor:

We recognize that there are many expert aquarists among our readers who may be successfully keeping all kinds of anemones. This, however, is a beginner article, so the species recommended and not recommended are geared for the beginner readership.


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Author Profile: Peter Steckley

Peter Steckley is a freelance science writer based in Calgary, Alberta, Canada. When he's not studying reef aquariums or testing out new recipes on his family, he's usually reading or enjoying the latest video game releases.