A large reef anemone living with anemonefish is possibly one of the most impressive communities in a reef aquarium.

Anemones or sea anemones are among the most striking anthozoa in tropical coral reefs. Like corals, anemones belong to the class of anthozoa and here to the subclass Hexacorallia. Real sea anemones belong to the order Actiniaria. Species from this order have a flat basal or pedal disc, a short column-shaped body and an oral disc surrounded by tentacles. The slit-like oral disc in the centre leads down to the spongocoel, the anemone’s stomach. The pedal disc has a strong muscle which the anemone uses to attach itself to rocks and to move about. The adhesive tentacles have stinging cells which they use to incapacitate and capture their prey. Although most commercially available anemones do have stinging cells which are unpleasant to the touch, they cause no problems in the aquarium.


©2011 Copyright by Daniel Heerz

However, some anemones do have such a potent toxin that they can cause humans considerable pain if they come into contact with the tentacles. The tree anemone Actinodendrum plumosum is one such example. Many anemones can even catch large fish thanks to their potent stinging tentacles. Aquarists claim that the Stichodactyla haddoni, a carpet anemone commonly available for sale, is even able to catch fish as big as a surgeon fish or a dwarf angel. On the Philippines a large Heteractis magnifica anemone was seen to catch an enormous crown of thorns starfish. That demonstrates the strength the anemones apply when catching food. One should never touch anemones in the sea with bare hands. The sting is so powerful that the skin affected can sting for months. It is therefore important when setting up an aquarium that the sting of the species selected will not harm the other invertebrates and fish or the aquarist. Ask a specialist supplier when choosing a harmless and yet magnificent species for the aquarium.

Anemones actually inhabit every marine area, from the Arctic regions to the Tropics. Anemones are often found particularly where favourable currents have allowed plankton to drift in. Most species are found in shallow waters in warm, temperate zones. Yet there are interesting species in the seas nearer home such as the Mediterranean and the North Sea, for instance the snakelocks anemones Anemonia sulcata and Actinia viridis. During deep sea research, scientists are always finding new species that have adapted to the particular environment. But new species are still always being found in tropical coral reefs.


©2011 Copyright by Daniel Heerz

Tropical anemones are of special interest to the aquarist. Like most corals, these usually harbour symbiotic algae in their tissue. Many anemones found in natural settings live in communities (symbiosis) with fish and prawns. Keeping both partners in symbiosis in an aquarium is an exciting challenge for the aquarist. Myriad different anemones and their partners live in tropical coral reefs at a depth that is readily accessible to divers (1 – 30 m). The greatest variety of species is found in waters from Indonesia to the Philippines. Reef anemones are among the most spectacular occupants of the reefs through their symbiosis with anemonefish. Individual anemones can be found even in shallow waters between seaweed and scree, for instance Heteractis malu which generally live in symbiosis with anemonefish. If a diver or snorkeler happens to come too close to an occupied anemone, the dominant female anemonefish will immediately dart out and vigorously defend her territory against all invaders or natural enemies. One of the most beautiful anemones is the Heteractis magnifica. This species, which lives on the reef slope, can grow to over a metre in diameter and lives in zones with very strong currents. Occasionally, this species will almost wholly retract in which case the nodular mantle lobes glow red or purple.

Reef anemones, whether solitary or living in groups, have fascinated aquarists since reef aquaria came into being. While anemones could often be kept for only a few months when aquarium keeping first kicked off, today some species will survive in an aquarium for many years, even decades. One reef anemone was even known to survive for over 30 years in an aquarium. An increasing number of species will even propagate in the aquarium through division.

Copyright Jürgen Wendel - Korallenzucht Wendel

Spectacular coloured species such as the red copper anemone Entacmaea quadricolor and the small carpet anemones Stichodactyla “minimaxi” replicate naturally in the aquarium by dividing. Division is one form of propagation which is presumably common to all anemones, another option which occurs in the natural habitat is sexual reproduction whereby the anemones release eggs and sperms. Some small anemones can even reach plague proportions as a result of what can only be described as invasive reproduction.

Glass anemones Aiptasia spp. and mini anemones Anemonia cf. majano, for example, have forced many an aquarist to clear his entire aquarium as they have reproduced so intensively as to oust all other invertebrates.

Let us look at the popular reef anemones again. There are many attractive species that are easy to keep in an aquarium. Reef anemones need plenty of light, a strong flow and occasional feeding to thrive. Fluorescent tubes, HQI spotlights and LED lights that are gradually gaining in popularity can be used today to illuminate the aquarium. The light requirements of most species are comparable to that of most soft corals and large-polyp stone corals.


Hybrid T-5 lamp with LED

Vividly coloured specimens such as Cryptodendron adhaesivum and Heteractis malu require very strong lighting. Phymanthus spp. anemones, on the other hand, need little light and only a mild current. How well anemones can be kept in an aquarium therefore depends very much on the respective species and their natural habitat. Blue lighting enhances the natural pigmentation and prompts the anemone to develop this further in the aquarium. It is important to generate a mild current; this can be achieved today with the sphere-shaped water pumps available. If the light and flow conditions are not right for the anemone, it will begin to move about the aquarium until it finds a suitable spot.

Consequently, you should protect the water pumps at least until the anemone has chosen its final position. A nylon stocking or filter tissue are suitable for this purpose. Aquarium heaters can also prove dangerous as the anemones can burn their pedal disc on them. Heaters should therefore be placed in the filter aquarium or padded to protect the anemone.

Anemones have no special demands in terms of mineral levels in the water. However, the water should be low in nitrates and phosphates. Anemones are not too sensitive to mild stress and can therefore be kept in aquaria with a high fish population. If anemonefish are kept together with an anemone, it is usually possible to keep marine angelfish and butterfly fish as the anemonefish, in their role as symbiosis partner, vigorously protect the anemone.

Regular feeding (1-2 times a week) with small amounts of frozen food stimulates the anemones to grow to surprizing dimensions.

Some species naturally move around the aquarium. The red base anemone Macrodactyla doreensis is one such example. This magnificent species which is found in myriad colors often wanders about and can damage other fixed invertebrates. If attention is paid to ensuring a favourable environment and, in the case of this species, a higher substrate, these excursions can be kept to a minimum, but not prevented completely. As a result, anemones need slightly larger or specialist aquaria. Small species are ideal for nano-aquaria.

All anemones are extremely sensitive while acclimatizing to the aquarium. The most common problems are injuries to the pedal disc when removing them from the reef or retailer’s tank followed by bacterial infections during transport. Once the anemone has become accustomed to the aquarium and found the ideal spot, all species are actually easy to keep and will enjoy a long life. Ideally, one should buy anemones from a reputable specialist retailer who acclimatizes his anemones carefully and can give sound advice on the needs of individual breeds.

The sting of most anemones can harm the other occupants of the aquarium. The anemone should therefore always be among the first animals to be placed in the aquarium. This allows it to move about in the aquarium at no risk until it has chosen its spot. Then the other corals can be placed, maintaining a sufficiently safe distance. Species that live on the substrate need deeper sand and stones on the ground in order to be able to take a foothold. Free-standing species look for a more exposed site in order to be able to develop to their full. A free-standing reef column is particularly ideal for allowing free-standing species to settle. The anemone can thus change position frequently without touching or stinging the other corals. Some fish such as filefish, pipefish, sea horses, boxfish and other slow-moving species are not suitable for socialization. Unfortunately, these species are more likely to be stung by the adhesive tentacles and captured as prey. Socialization is more successful with any fleet and nimble species.

Anemonefish settle in most types of anemone in tropical coral reefs. Anemone symbiosis with fish fascinates both scientists and aquarists. Interest in these communities has also spread among non-aquarists since the film „Nemo“. The fish are protected from the stinging tentacles thanks to the skin mucus that the anemone’s tentacles constantly produce. This protection does not come naturally, i.e. the fish have to gradually build up and constantly renew their defence. On the reef, both partners benefit from this interesting community. The fish develops a protective shell and, in return, protects the host anemone from natural enemies such as butterfly fish. Tiny damselfish often live on reef anemones, even alongside anemonefish. In the Mediterranean, the Bucchich's goby lives in the snakelocks anemone which has a powerful sting.

Porcelain crabs and various types of prawns also live in harmony with anemones, for instance Periclimenes and Neopetrolisthes. One quite spectacular feature is the symbiosis of the hermit crab which allows anemones to settle on its shell in an effort to protect itself from natural enemies such as the Dardanus pedunculatus.


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