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, up to about 11" (30 cm) tall and 6.5" (17 cm) wide, and are 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 a marine 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. Hence, they are also known as the Giant Green Pacific Sea Anemone and Green Surf Anemone.

Giant Green Anemones that are left out of water when the tide recedes will force the water out of their body cavity, 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.

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
Data provided by GBIF.org
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: 20 gal (76 L)
  • Aquarist Experience Level: Expert
  • Temperament: Semi-aggressive
  • Temperature: 59.0 to 72.0° F (15.0 to 22.2° C)
  • Size of organism - inches: 6.5 inches (16.51 cm)
  • Diet Type: Carnivore
  • Suitable for Nano Tank: Yes

Habitat: Distribution / Background

The Giant Green Anemone Anthopleura xanthogrammica was described by Brandt in 1835. It is found in waters from Panama (in areas with cold water), up to the Pacific Coast line, and then on to Alaska. This anemone is not on the IUCN Red List for endangered species. Other common names it is known by include the Giant Green Pacific Sea Anemone, Green Surf Anemone, Giant Green Sea Anemone, and Green Sea Anemone.

The Anthopleura genus is a member of the Actiniidae family and currently contains 52 species. General common names the Anthopleura genus is known by are the Aggregating Sea Anemone and Aggregating Anemone. 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

The Giant Green Anemones are found in colder waters. They are found solitary or in small groupings on vertical rock walls that are shaded, sand and rock covered shore lines, and tidal pools. They occur in tide pools exposed to the air at low tide. They will retract their tentacles and close up into a globule ball when the water level drops during low tides. They can also be found in deeper waters, down to depths of 98.5 (30 m) feet.

This cold water anemone feasts on sea urchins, small fish, crabs, star fish and dislodged mussels. They use their venomous cells, or nematocysts found in their tentacles, to sting and deflect any possible threats or attacks. Predators of the Giant Green Anemone includes the Sea Mouse Aeolidia papillosa, the Tinted Wentletrap Epitonium tinctum, and a sea star known as the Leather star Dermasterias imbricata.

  • Scientific Name: Anthopleura xanthogrammica
  • IUCN Red List: NE - Not Evaluated or not listed

Description

Giant Green Anemones can grow up to 6.5” (17 cm) in diameter and can reach as tall as 11” or more (30 cm), yet it is unknown how long they live. Some anemones can be hundreds of years old in the wild. In captivity, there are anemone species known to live 80 years or more.

The colors of the Giant Green Anemone are very pretty. The pedal column is olive green to brown topped with a crown of tentacles that are greenish, bluish, or white with no bands or markings. The oral disc can be green, gray, brown or blue.

This beautiful sea anemone has a symbiotic relationship with an algae, known as zooxanthellae, 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.

They have soft squishy bodies that are flat when open. The base, 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 tentacles are are short, thick, and taper at the ends. They will be in 6 or more rows along the margin surface of the oral disc, with the mouth being in the center. The Anthopleura genus take food in and expel waste through this same opening. The mouth should be closed and tight. It will open when hungry, having an oval look. A gaping mouth is a warning signal of possible pour health.

  • Size of organism - inches: 6.5 inches (16.51 cm) - Can reach 6.5” (17 cm) in diameter and 11” or more (30 cm) in height.
  • Lifespan: 80 years - It is unknown how long they live, but some anemones can be hundreds of years old in the wild, and in captivity have been known to last 80 years or more.

Difficulty of Care

This anemone is rarely, if ever, available to aquarists through retailers, and in many areas they are banned from collection. The Anthopleura genus can be difficult to care for and are best left in the wild. However, if for some reason they become available, then they are best left to expert aquarists. 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 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 transfer 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 its 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.

To transfer an Anthopleura specimen 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 while tickling the foot can work.

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

Foods and Feeding

The Giant Green Anemone is a carnivore. In the wild they primarily eat urchins, small fish, crabs, and dislodged mussels. However, there are even pictures of one eating an Ochre Starfish! 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.

The metabolism of the Anthopleura species are not as fast as warmer water anemones. They are cooler water creatures, so usually only need to be fed once or twice a month.

  • Diet Type: Carnivore
  • Flake Food: Occasionally - Carnivore preparations if they like it.
  • Tablet / Pellet: Occasionally - Carnivore preparations if they like it.
  • Live foods (fishes, shrimps, worms): Some of Diet - From marine sources.
  • Liquid Foods: Some of Diet - Zooplankton.
  • Meaty Food: All of Diet - Sources of marine flesh and frozen/thawed preparations for carnivores.
  • Feeding Frequency: Seldom - Feed only once or twice a month.

Aquarium Care

Water changes of 10% bi-monthly or 20% a month are typical. Monitor your water quality for your particular situation and adjust your water changes accordingly. Waste production created by your anemone can be calculated in inches. Basically, every inch of anemone is equal to an inch of fish, so an average-sized Giant Green Anemone produces a bio-load equivalent to that of about two 3" fish.

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. Additional chemical additives, such Chemi-Pure, GFO, and carbon also help maintain quality water parameters. Poly-fiber can be cut and used in sumps, etc. A good protein skimmer is a must.

Although anemones are not as dependent on calcium as stony corals, magnesium and calcium is still needed to keep the pH and alkalinity stable and within the correct parameters. Additions of trace elements are suggested. Phosphates should be kept around 0.03 or less. Control phosphates with products such as Phosban and the Phosban reactor. Phosphates should be less than 0.03 ppm.

  • Water Changes: Bi-weekly - Water changes of 10% twice a month, or 20% a month are typical.
  • Calcium Levels: 380.0 - 450.0 ppm - Helps to balance alkalinity. Aim for 420 ppm, or 385 ppm if you are using Seachem calcium.
  • Alkalinity Levels: 7.0 - 11.0 dKH - Aim for 10 dKH (3.5 meq/l) for reef tanks.
  • Magnesium Levels: 1,250.0 - 1,350.0 ppm - Test magnesium levels and adjust before checking calcium.
  • Strontium Levels: 5.0 - 15.0 ppm - Aim for 8 ppm.
  • Iodine Levels: - .030 to .060 ppm: Control is not recommended.

Aquarium Setup

The Giant Green Anemone can be kept in a nano reef of just 20-gallons or more. The typical reef environment is needed, but it must be a cold water reef. They should be placed on live rock or some other solid material they can attach to. However, because calcium doesn't need to be as high in cold water, providing reef rock for calcium is actually not necessary.

Because bacterial formations take a very long time in cooler water, the most important thing for the nano reef is mechanical and chemical filtration. Provide a good skimmer and use filter floss and chemical additives, such Chemi-Pure, GFO, and carbon in the filter to help keep the water clean. Chemi-Pure helps remove heavy metals, copper, phenol, ammonia and other nitrogenous waste. It also helps keep the pH at a consistently safe range. Granular ferric oxide, or GFO, helps with phosphate control. The addition of a refugium with a deep sand bed can help maintain normal parameters.

They need moderate water movement and strong lighting. The light emitted from LED and t5 fixtures puts off less heat, which is essential with a cold water tank. It is suggested to keep temperatures from 55 to 60°F (12.7 - 15.5°C), which allows for you to have both inter-tidal and sub-tidal animals. A chiller will be needed, but keep the temperature stable, as fluctuations can be stressful to the anemone. Acrylic tanks are best for insulating against temperature fluctuations, each 1/2" will give a thermal barrier of 5° F. Be sure to have all of your pumps covered, most good quality pumps have guards on them.

  • Minimum Tank Size: 20 gal (76 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

The Giant Green Anemone is considered semi-aggressive because they can be mobile, and possibly split. It has often been suggested to not put anemones in a reef environment since corals cannot move away from the stinging tentacles. Most of the cold water anemones will stay still if their needs are met. They will move, however, if your lighting is not good or the water quality is not to their liking.

After splitting, anemones will tolerate their own “clones” and sometimes their own species. All anemones in the tank need to have their own space, otherwise there can be a “chemical” warfare between species. This will usually cause one to not eat, shrink and eventually die.

Giant Green Anemones are best kept in a species specific display. Keeping corals in the tank can be a risky thing to do because they will sting everything they can reach, like corals and other invertebrates. Anemones will move if your lighting is not good, or the water quality is not to their liking. If attempting to add cold water corals, allow the anemone several months to settle first. Once they are in place, you can then try placing a coral away from them.

If the tank is very large, keeping larger cold water fish should be fine. Problems occur when keeping small gobies, blennies or other small cold water fish. These can easily become dinner if they wander into the very sticky (more sticky than typical) tentacles of this anemone. Be cautious with other tankmates, too, as this beautiful anemone does eat many invertebrates that wander their way.

  • Venomous: Yes
  • Temperament: Semi-aggressive
  • Compatible with:
    • Same species - conspecifics: Sometimes - They may tolerate their own offspring.
    • Anemones: Threat
    • Mushroom Anemones - Corallimorphs: Threat
    • Leather Corals: Threat
    • Zoanthids - Button Polyps, Sea Mats: Threat
    • Sponges, Tunicates: Threat
    • Shrimps, Crabs, Snails: Monitor - Only cold water species and commensal animals.
    • Starfish: Threat
    • Feather Dusters, Bristle Worms, Flatworms: Threat
    • Clams, Scallops, Oysters: Threat - This anemone will quickly multiply and sting tankmates
    • Crabs: Monitor
    • Snails: Threat
    • Sea Apples, Cucumbers: Threat
    • Urchins, Sand Dollars: Threat
    • Nudibranch, Sea Slugs: Threat
    • Copepods, Amphipods, Mini Brittle Stars: Safe
    • Stony Corals: Threat - is aggressive
    • Soft Corals: Threat - is aggressive

Sex: Sexual differences

No sexual difference in appearance is noted.

Breeding / Reproduction

Giant Green Anemones should divide in captivity, but they have not been bred in captivity. There is no information on the captive propagation of cold water anemones, it may be similar to other anemones. Other cold water anemones may reproduce by fission or external fertilization of egg and sperm.

These cold water anemones are known to reproduce by external fertilization of egg and sperm. They shed mature gametes into the coelenteron, their central digestive cavity, which are then spawned through the mouth. The fusion of two gametes creates a zygote, which develops into a planktonic planula larva. The larva floats away and begins early morphogenesis of tentacles, septa and pharynx. Then eventually it finds a spot to land, such as established mussel beds, where it will attach and develop a pedal disk, growing 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.

Giant Green Anemones do have predators in the wild that include sea snails and sea spiders. Some natural predators include 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 anemone's tentacles. A sea star known as the Leather star Dermasterias imbricata will also consume this anemone.

Availability

The Giant Green Anemone, as well as other Anthopleura species, are very rarely for sale from retailers, 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 to find out if they are protected there.

References

Author: Clarice Brough CFS, Carrie McBirney
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