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Anemones: Sea Anemone - Tube Anemone

Sea Anemone Facts About the Sea Anemone Species
Actiniaria and Ceriantharia
Sea anemone picture of an White Spotted Rose AnemoneWhite Spotted Rose Anemone Urticina lofotensis Photo © Animal-World

   A sea anemone is often called the "flower of the sea", and like flowers they are quite beautiful and varied, but they are actually animals!

Sea Anemone Facts:

   A beautiful sea anemone living with a colorful clownfish is a saltwater aquarium favorite! There are over 1100 described species of sea anemones and we are still being surprised by the discovery of new species. A most recently discovered species, an Antarctic sea anemone from the South Shetland Islands Stephanthus antarcticus, was found and described by Rodriguez & Lopez-Gonzalez in 2003.

   Anemones are invertebrates, as are 95% of the earth's creatures. Invertebrates are animals without backbones and most invertebrates are insects. However saltwater animals like sea anemones, corals, shrimps, snails, and crabs are also invertebrates. Anemones are stinging animals that live their entire lives as a polyp, with the only exception being a short larval stage for some species.

   Keeping sea anemones in captivity began way back in 1881, when the first anemone specimen was housed in a tub. A more intimate and dedication interest evolved in the mid-20th century. During this time, advances in SCUBA diving along with international jet transportation, made sea anemones much more available and they began being kept in reef aquariums around the world. They are also used as a food source by people in some areas of the Indo-Pacific and the Mediterranean, eaten as boiled or spiced anemones.

   Once established, many types of anemones are known to be quite hardy. However many anemones simply do not fare well in captivity. Much of their demise is attributed to the difficulty in the collection and handling of these delicate animals, but it can also often be attributed to their care after being obtained by the aquarist.

For information about setting up a reef tank see: Reef Tanks - Mini-Reef Aquarium Basics

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Adhesive Sea Anemone, Cryptodendrum adhaesivum & Porcelain Crabs
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Great video showing two beautiful animals.

The Adhesive Sea Anemone, also called the Sticky Anemone is a host to a wide variety of marine life. They host clownfish, some crabs and damsels. They resemble a pizza, having what looks like an outer crust and a contrasting center. Provide 100 gallons, bright lighting and clean water. The tank should be mature, around a year old and plenty of space for their eventual 12" size. Target feed your anemone a variety of minced foods on a regular basis.

Adhesive Sea Anemone, Cryptodendrum adhaesivum in the wild
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Massive mature anemone hosted by ornary striped damselfish!

This video give some perspective as to the size that the Adhesive Sea Anemone can grow to. They are being hosted by 2 clownfish and are being rivaled by a larger black Domino Damsel and some juveniles for the spot! Do not rely on your clownfish or damsel to feed your anemone enough food. In captivity, there is not the same amount of zooplankton as there is in the wild, which they feed on, so you will have to feed them regularly.

Hell's Fire Anemone, Actinodendron plumosum, & Harlequin Crab Pair
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Up close and personal with some marine symbiosis!

The Hell's Fire Anemone differs in a few ways from other anemones. While they need good light, a mature tank and good meaty foods, they do not play well with others. The Hell's Fire Anemone will sting all other corals with a sting that is much more potent than many other anemones. This anemone will not host clownfish, only inverts, like for instance... Harlequin Crabs! They make a great addition to a species specific tank!

Banded Tube Dwelling Anemone, Pachycerianthus maua
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A Banded Tube Anemone in the wild

Making their debut after lights are out, the Banded Tube Anemone emerges to feed on small prey. Do not feed large chunks of food as it can damage the tentacles. They need very clean water that is highly oxygenated. This oxygen is best provided by ozonizers since a strong water current is not tolerated. These anemones make very long and wide tubes and a very deep sand bed. They are best left to experts or just left in the wild.

Beaded Sea Anemone, Heteractis aurora
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Wild specimen with clownfish family!

This anemone has been referred to as the nursery anemone and it is easy to see why in this video. The Beaded Sea Anemone will host the parents and several juveniles at the same time. They have typical needs as other anemones, which is a mature tank, strong lighting, high water quality and lots of food! Since they like to burrow in the sand, keep an eye out for bristle worms, since they have been known to annoy and chew at this genus of anemones.

Beadlet Anemone, Actinia equina
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Video of anemone slowly opening

The Beadlet Anemone is about as bullet proof as you can get when it comes to an anemone! While you can have several in one tank, they should not be near each other unless they are offspring (division). If cared for properly, they will reproduce internally, releasing live baby anemones in different colors! How cool is that! They are fin in a tank that is 20 gallons or more and they are only 2" in size on average. Do not confuse them with the Waratah Anemone (Actinia tenebrosa) which is a cold water anemone that will die in our tropical tanks! The Beadlet Anemone, A. equina can tolerate waters from 35 to 82˚F (1.7 to 27.8˚C)!

Brown Glass Anemone, Aiptasia pallida
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Awesome video of Peppermint Shrimp eating this pest anemone

Brown Glass Anemones will quickly become the scourge of a captive environment! There are True Peppermint Shrimp that will eat this pest, however if they have plenty of other foods to choose from, they may not be as affective. These anemones will reproduce like rabbits, sting corals and fish and make a new aquarist just give up! Quarantining live rock and all new corals is the best prevention since these little buggers can slip and hide into the smallest opening under a coral edge or in any rock!

Bubble Tip Anemone, Entacmaea quadricolor brown color
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Cool time lapse movement of a Bubble Tip!

The Bubble Tip Anemone is a mobile reef animal that uses a muscular foot to move. If fed well, with small pieces of fresh marine flesh and they have good light and water flow, they will stay in the same spot. If water quality is low or the tank is less than a year old, it will walk around, "looking" for better conditions and can sting other corals or get chopped up in an uncovered intake of a pump. Clownfish should be 1/2 the size of the anemone or this will stress the anemone out. A great "beginner" anemone, this is still best kept by intermediate aquarists.

Bubble Tip (ROSE) Anemone, Entacmaea quadricolor
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Captive Bubble Tips on display

The Rose Bubble Tip Anemone is arguably one of the most sought after of this species. They can range from a deep burgundy red to a mix of green and red. They split quite often and tend to roam more so than the other colors for some reason. Personally, feeding them every other day shrimp or other meat foods chopped up into small pieces and good light will keep them still. For some reason, some will die if given a silverside to eat. Not all, but a green one that I had did die! Take should be mature, over a year old before adding any anemone. These will usually split before they get too large, making them great for selling to defer the expense that this hobby brings.

Sea anemone habitat

   These fabulous colorful animals are found in coastal waters throughout the world. Anemones live in shallow waters including the coral reefs, and in the deep oceans. They live in both tropical waters and cold waters.

   Anemones are benthic, which means they are attached to rocks or the sea floor. They mostly stay in one place waiting for fish or other prey to swim by close enough for them to ensnare them in their venom filled tentacles. In the aquarium they will often move around until they find a place that they like and then stay put.

Appearance of a Sea Anemone

   Anemones have a body that is radically symmetric, but other than that they come in many shapes, sizes, and colors. They come in a wide variety of colors and are usually about 1 to 4 inches (2.5-10 cm) across, but a few species can be as small as half an inch (1.25 cm) across or as large 6 feet (1.8 m) across. The largest and most brilliantly colored anemones occur in coastal tropical waters

Sea Anemone Facts

   Taxonomy - Classification: To better understand what sea anemones are, we can gain valuable clues from their scientific classification.

  • Kingdom: Animalia
  • Phylum: Cnidaria - "to sting"
       The phylum Cnidaria includes anemones, corals, jellyfish, and hydras. The term Cnidaria (with a silent "c") means "to sting", and this name refers to the cnidae, or nematocysts, which all Cnidarians have. The 'cnidae' are the stinging cells, which provide these animals a means of capturing prey and/or defending themselves from predators by inducing a painful sting.
       Another phylum name (older) for the Cnidarians is Coelenterata (pronounced "se-len-ter-a'-ta'). This name is from their old phyletic grouping, and may still be used informally in some settings when referring to these animals. Coelenterate refers to the single body cavity that serves as stomach, lung, intestine, and everything else! There is only one opening into this cavity, the mouth, through which everything passes in and out. The mouth is surrounded by several or many tentacles, which contain the nematocysts (cnidae) at their tips.
  • Class: Anthozoa - "flower-like animals" 
       Anemones are placed in the Anthozoa class of single or colonial polyps along with corals, sea fans, and sea pansies. The sea anemones are sometimes referred to as the ‘flowers of the sea'. They can be very colorful and can appear similar to flowers, but they are not plants. They are actually predatory, meat eating animals.  Interestingly their common name ‘anemone' is derived from a group of terrestrial plants in the buttercup family. The plant genus Anemone consists of about 120 species of very pretty flowering plants.

   Sea anemones Life Cycles: There are two methods by which sea anemones can reproduce, either by sexual reproduction or by lateral fission.

  • Sexual reproduction:
    Sexual reproduction is where the anemones release eggs and sperm into the water, which then producing free-swimming larvae.
  • Lateral fission:
    Lateral fission is a system of budding, where an identical animal sprouts from the side of the parent anemone, growing until it can survive on its own. Because of its ability to reproduce by lateral fission or budding, pieces of an anemone can turn into new sea anemones.

   Anemones are long-lived animals, with some species of sea anemone living 50 years or more.

Types of Sea Anemones

The next level of classification for sea anemones is the Order. This is where types of sea anemones begin to diverge:

  • Order: Actinaria - Sea Anemones or 'True Anemones'
       Sea Anemones are in the order Actinaria, and are often called the "true anemones". They have an adhesive pedal disc or foot used to hold them in place and a hollow cylindrical or column shaped body. They have an oral disc with a mouth at the top which is surrounded by a circle of tentacles containing stinging nettle-cells or nematocysts.
       Their stinging cells are used to capture prey and push it into its mouth. With only a slight touch, the tentacles shoot harpoon-like filaments into passing prey, injecting it with a paralyzing neurotoxin, and then guiding it into the mouth.
  • Order: Ceriantharia - Tube Anemone or Burrowing Sea Anemone
       Tube Anemones are in the order Ceriantharia. They are also known as Tube-dwelling Anemones or the Burrowing Sea Anemone. They are solitary animals, living and withdrawing into tubes buried that are buried in soft sediments.
       Tube Anemones look very similar to sea anemones, but they have elongated bodies adapted for burrowing and they lack the pedal disc or foot. The cylindrical shaped body is covered by a tube of secreted mucous and is usually hidden in the muddy substrate. The mouth is on a central disk, surrounded by short tentacles in the center and longer tentacles on the margins. Usually only the tentacles are visible above the ground.

Sea Anemone Care

  •  Zooxanthellae:
       Most anemones survive in a symbiotic relation with with marine algae called zooxanthellae. The zooxanthellae are photosynthetic organisms whose waste products are used by the anemone for food. Since the zooxanthellae require light to carry on photosynthesis, anemones in turn require bright light to thrive in the aquarium.
       The zooxanthellae are generally a light brown color, the same color as the light brown leather corals that also harbor zooxanthellae. The loss of zooxanthellae, apparent by a whitening of the anemone, usually means the anemone will slowly grow smaller and smaller until it dies.
  • What do sea anemones eat:
       Sea anemones are carnivores, meaning they are meat-eating animals. Though they obtain most of their nutrition from zooxanthellae, symbiotic algae that lives inside their tissues, they will also eat other proteins. Sea Anemones will eat fish, mussels, worms, shrimp, and zooplankton like copepods, isopods, amphipods, and other small crustaceans, and tiny marine larvae. In order to eat, they must wait for their prey to swim by, then sting and ensnare it with their tentacles, and finally guide it into their mouth
  • Marine lighting - how much light for anemones:
       Many anemones need lots of light to do well. They need light to support zooxanthellae, symbiotic algae that live inside their tissues and from which they obtain most of their nutrition.  Provide 2 to 5 watts per gallon, preferably with some blue spectrum provided by actinic light bulbs or higher temperature metal halide lighting. The scale of light intensity is:
    • Low level - 1 to 2 watts per gallon, about a normal marine setup with regular fluorescent bulbs (10 watts per foot bulbs).
    • Medium level - 2 to 4 watts per gallon, maximum regular fluorescent to minimum VHO or metal Halide.
    • High level - 5 or more watts per gallon, maximum VHO and/or metal halide. See Mini-reef: Lighting for a description of VHO and metal halide

Sea Anemone Predators

   There are few sea anemone predators. When an anemone feels threatened, it will pull its tentacles into its body giving it a round ball-like appearance. Though there are very few animals will eat anemones, there are some that do prey on them. Anemone predators include:

  • nudibranchs
  • snails
  • fish
  • sea stars

   Some specific predators are the Grey Sea Slug Aeolidia papillosa, which feeds exclusively on sea anemones, and also the Tompot Blenny Parablennius gattorugine, which enjoys snacking on them if it gets a chance.

Author: Clarice Brough, CFS