Giant Green Anemone

Giant Green Pacific Sea Anemone, Green Surf Anemone

Giant Green Anemone, Anthopleura xanthogrammica, Giant Green Pacific Sea Anemone, Green Surf AnemoneAnthopleura xanthogrammicaPhoto © Animal-World: Courtesy David Brough

The brilliant green coloring of the magnificent Giant Green Anemone gets even greener under bright sunlight!

The Giant Green Anemone Anthopleura xanthogrammica is one of the most spectacular anemones. They can be quite large and very green. They look somewhat like a plant or flower, but they are actually animals. This beautiful sea anemone has a special symbiotic relationship with an algae living in its tissues. This algae, called zooxanthellae, provides nourishment for the anemone with proper lighting. Under strong sunlight the algae is encouraged to grow and the sea anemone gets very green. When the anemone lives in more shaded areas the algae's growth is inhibited. Then the anemone is less colorful, sometimes being almost white.

You can find Giant Green Anemones along the shoals of the Pacific Coast line. They live in mid to low intertidal zones where there is strong wave action and surge. They can be found hiding in crevices, on the sides of rocks, or under rocks.

Green Surf Anemones that are left out of the water when the tide recedes will force the water out of their body cavities, pull in their tentacles, and fold inward for protection until the return of the tide. At this time they are not very pretty, looking more like globular blobs or muddy donuts rather than pretty green anemones. But no matter where or how you find them it is best to leave them be. These sea anemones need cold water to survive rather than the tropical temperatures of most hobbyist's saltwater aquariums, and in many areas they are banned from collection.

The Giant Green Anemone is generally used in research and has proven very useful to the medical community. It is contributing to the development of heart medications. A compound from this anemone is now used as a vertebrate heart stimulant.

For more about the types of Sea Anemone Species, see:
Sea Anemone - Tube Anemone

Geographic Distribution
Anthopleura xanthogrammica
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Giant Green Anemone, Anthopleura xanthogrammica

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Anemone reacting to the tide

The Giant Green Anemone was banned from collection, however their numbers have increased over the years. They are a cold water anemone which does not host clownfish and will eat any meaty morsel that floats its way. During low tide, they will pull their tentacles inward and form a small globular ball as it waits for the sea to return, hopefully with dinner!

Giant Green Anemone - Quick Aquarium Care
  • Minimum Tank Size: 10 gal (38 L)
  • Aquarist Experience Level: Expert
  • Temperament: Semi-aggressive
  • Temperature: 59.0 to 72.0° F (15.0 to 22.2° C)
  • Diet Type: Carnivore
  • Suitable for Nano Tank: Yes

Habitat: Distribution / Background

Sea Anemone Facts: Anthopleura xanthogrammica was first described by Brandt in 1835. The Anthopleura genus is a member of the Actiniidae family and this genus contains 52 species. The Anthopleura xanthogrammica is not on the IUCN Red List for endangered species.

Where are Sea Anemones Found: The Giant Green Anemone, also known as the Giant Green Sea Anemone, Green Surf Anemone, Giant Green Pacific Sea Anemone, and Green Sea Anemone, is found in waters from Panama (in areas with cold water), up to the Pacific Coast line, and then on to Alaska.

Sea Anemone Habitat: Giant Green Anemones are found in colder waters on vertical rock walls that are shaded, sand and rock covered shore lines and tide pools. They are found solitary or in small groupings. They will actually retract their tentacles and close up if the water is sparse during low tides. This cold water anemone feasts on sea urchins, small fish, crabs, and dislodged mussels. They use their venomous cells or nematocysts found in their tentacles to sting and deflect any possible threats or attacks.

Sea Anemone Species: There are 52 different species in this genus. General common names the Anthopleura genus is known by are the Aggregating Sea Anemone, Aggregating Anemone. The common names of some of the other best known Anthopleura species include:

  • Anthopleura ballii - Red-speckled Pimplet Anemone, Pimplet Anemone
  • Anthopleura elegantissima = Aggregating anemone, Aggregating Sea Anemone
  • Anthopleura sola = Solitary Anemone, Sun Anemone
  • Anthopleura artemisia = Moonglow anemone, Burrowing Green Anemone, Buried Anemone, Burrowing Anemone
  • Anthopleura elegantissima = Aggregating Sea Anemone
  • Scientific Name: Anthopleura xanthogrammica
  • IUCN Red List: NE - Not Evaluated or not listed


Appearance of a Sea Anemone: Giant Green Pacific Sea Anemones can grow up to 6.5" (17 cm) in diameter and can reach as tall as 11" or more (30 cm). They have soft squishy bodies that are flat when open. The bottom, or pedal column, has a sticky foot that they use to adhere to various surfaces. They also use this "foot" to move around if conditions are not ideal. The color of the column is olive green. The tentacles will be in 6 or more rows along the margin surface of the oral disc, with the mouth being in the center. The tentacles are short, thick and taper at the ends. They are usually light green. The mouth should be closed and tight. The mouth will open when hungry, having an oval look. When open, a gaping mouth is a warning signal of possible poor health. The Anthopleura genus take food in and expel waste through this same opening.

The colors of the Giant Green Anemone are very pretty. The color of the column is olive green to brown topped with a crown of tentacles that are greenish, bluish, or white with no bands or markings. The Disc can be green, grey, brown or blue. This beautiful sea anemone has a symbiotic relationship with an algae living in its tissues. When provided strong sunlight the algae is encouraged to grow and the anemone becomes very green. When the anemone is in more shaded areas the algae is inhibited, so the anemone is less colorful, sometimes almost white.

Sea Anemones Life Cycles: It is unknown how long they live, in fact some anemones can be hundreds of years old in the wild, and in captivity have been known to last 80 years or more.

  • Size of organism - inches: - They can grow up to 6.5" in diameter and reach 11" tall.
  • Lifespan: - Their lifespan is unknown, however some anemones have reached 80 years in captivity and can live hundreds of years in the wild.

Difficulty of Care

Sea Anemone Care: This anemone is rarely, if ever, available to aquarists, as in many areas they are banned from collection. If for some reason they become available, the Anthopleura genus can be difficult to care for. They must be in cold water and do have good lighting needs. A saltwater aquarium should be at least 6 months old and stable before adding a new Giant Green Anemone.

When choosing an Anthopleura genus anemone, make sure the color is good, the mouth is not gaping open, and the foot and tentacles are sticky to the touch. An Anthopleura should be attached to something. Make sure the foot area is not damaged because of the anemone being pulled off its surface.

To take an Anthopleura from another aquarium, use a very thin blunt item like a credit card to get under the foot. Slowly nudging it away will get the anemone off the glass. If it's attached to a rock, ideally you can simply purchase the rock as well. If you cannot purchase the rock then directing water at it or wiggling the rock gently upside down under water while tickling the foot can work.

  • Aquarium Hardiness: Difficult to Impossible
  • Aquarist Experience Level: Expert

Foods and Feeding

What Do Sea Anemones Eat: The Giant Green Anemone is a carnivore. In the wild they eat urchins, small fish, crabs, and dislodged mussels. In captivity you can feed your anemone chopped silversides, shrimp, krill, and mussels, fresh chopped fish (from your grocery store), as well as frozen carnivore preparations. Because cold water anemones have much slower metabolisms, feed only once a week or twice a month.

  • Diet Type: Carnivore
  • Meaty Food: All of Diet - They can be fed chopped silversides, shrimp, krill, and mussels, fresh chopped fish (from your grocery store), as well as frozen carnivore preparations.
  • Feeding Frequency: Seldom - Feed only once or twice a month.

Aquarium Care

Water changes of 10% bi-monthly or 20% a month are typical, but monitor your water quality for your particular situation and adjust your water changes accordingly. One of these average sized anemones is equal to one fish as far as waste production is concerned. Purigen and Poly-fiber are great products to help in maintaining water quality. Purigen is a synthetic polymer that removes soluble and insoluble impurities from water at an exceptionally high rate and capacity, helping to control ammonia, nitrites and nitrates. Additions of Iodine and and trace elements are suggested.

  • Water Changes: Bi-weekly
  • Iodine Levels: - Additions of Iodine and and trace elements are suggested.

Aquarium Setup

The typical reef environment is what is needed for your anemone; i.e. live rock in a reef environment for cold water. They should be placed on live rock or some other solid material they can attach to. Be sure to have all of your pumps covered. Most good quality pumps have guards on them and are worth the investment.

  • Minimum Tank Size: 10 gal (38 L)
  • Suitable for Nano Tank: Yes
  • Live Rock Requirement: Typical Amount
  • Substrate Type: Any
  • Lighting Needs: High - Strong lighting - They will be a more intense green with strong lighting.
  • Temperature: 59.0 to 72.0° F (15.0 to 22.2° C)
  • Specific gravity: 1.023-1.025 SG
  • Water Movement: Moderate
  • Water Region: Bottom

Social Behaviors

All anemones are semi-aggressive. After splitting, anemones will tolerate their own "clones" and sometimes their own species. Otherwise there will be "chemical" warfare with other species of anemones. This will usually cause one to not eat, shrink and eventually die. Because anemones can be mobile, it has often been suggested not to put them in a reef environment since corals cannot move away from the stinging tentacles.

Once you have your anemone situated and it has not moved for several months, it might be safe to add other corals. This is a "proceed at your own risk" type situation. Keep in mind that there are situations that will encourage your anemone to move. If your lighting is not sufficient they will move. If your water movement is not to their liking they will move. Also if your water quality is not good, they will move or let go and float around.

  • Venomous: Yes
  • Temperament: Semi-aggressive
  • Compatible with:
    • Same species - conspecifics: Sometimes
    • Anemones: Monitor
    • Mushroom Anemones - Corallimorphs: Monitor
    • Leather Corals: Monitor
    • Shrimps, Crabs, Snails: Monitor
    • Starfish: Monitor
    • Crabs: Monitor
    • Snails: Monitor
    • Nudibranch, Sea Slugs: Monitor
    • Stony Corals: May be aggressive
    • Soft Corals: May be aggressive

Sex: Sexual differences

No sexual difference in appearance is noted.

Breeding / Reproduction

Giant Green Anemones have have not been bred in captivity. There is no information on the captive propagation of cold water anemones, but it may be similar to other anemones.

These cold water anemones reproduce by external fertilization of egg and sperm. They spawn from September to November, producing larvae that float away, eventually finding a spot to land, such as established mussel beds. They then attach and develop a pedal disk that grows into a new anemone.

  • Ease of Breeding: Difficult

Ailments / Diseases

Problems for the Giant Green Anemone are pretty minimal unless your lighting, water movement, feeding and water quality are low. Then your anemone will detach to look for "better conditions." This usually results in an unpleasant experience with a water pump.

Sea Anemone Predators: These anemones do have predators in the wild that include sea snails and sea spiders. Some natural predators are the Sea Mouse Aeolidia papillosa which is a a sea-slug or nudibranch and a snail called the Tinted Wentletrap Epitonium tinctum that feeds on the tentacles. A sea star known as the Leather star Dermasterias imbricata will also consume this anemone.


Buy A Sea Anemone: The Giant Green Anemone, as well as other species in the Anthopleura genus are very rarely for sale making them generally unavailable to aquarists. Collection is also restricted in many areas. Before collecting them, be sure to check with local authorities in the area you are in to find out if they are protected there.


Author: Clarice Brough CFS, Carrie McBirney
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