Clownfish and their anemones are popular aquarium subjects, never failing to capture the attention of all who view them. Yet they are widely misunderstood. Before com mitting to creating an aquarium for them, one should consider their special needs.
THE HOST ANEMONES. Given its powerful stinging tentacles and its demanding care requirements, the anemone is the Pivotal Species in the aquarium community. Three families of anemones are represented among the clownfish hosts. One,Thalassianthidae, is of minimal interest. Of the remaining two families, Actiniidae is relatively easy to manage in the reef aquarium, while Stichodactylidae is rather difficult.
Family Actiniidae. Hardiness is a characteristic of the two actiniid anemones that host clownfishes and makes them good choices for the beginning aquarist who wants to set up a clownfish/host anemone tank. These are Macro-dactyla doreensis and Entacmaea quadricolor. Macrodactyla is known to the aquarist as Long Tentacle Anemone, often abbreviated simply as LTA. The red column topped with bluish gray verrucae is distinctive, although in a proper habitat tank, the column will be buried, as it is in the ocean. The long tentacles — gray, bluish, or pinkish in color — often twist into a spiral shape, leading Fautin and Allen (1986) to call this the Corkscrew Anemone. It hosts only three clownfish species in nature, but in the aquarium will be accepted by others. Its range is also restricted, with the majority of specimens collected from Indonesia. LTA is a widely available clownfish host and is reasonably hardy, but it does need a suitable substrate in which to bury its column. Lacking this, it will wander around, fail to attach, and eventually die. It is most frequently found in mud, in water less than 15 feet deep. Mud implies moderate current, and shallow water suggests the need for bright illumination.
Entacmaea quadricolor, called the Bulb, Bubble Tip, or Maroon Anemone in the aquarium trade, holds the record
Skunk Clowns (Amphiprion perideraion) with huge Magnificent Anemone (Heteractis magnifica) on current-swept slope.
206 Natural Reef Aquariums for clownfish species hosted, at 13. The inflated tips of the tentacles, looking something like the nipples on old-fashioned glass baby bottles, are characteristic. No other
Maroon Clown pair (Premnas biaculeatus) in their Bubble Tip Anemone (Entacmaea quadricolor): the female clownfish is always larger.
anemone has this feature. The bulbs occur more commonly on anemones that have clownfish in residence than on those that do not. There are two types of Entacmaea, which may have important implications for aquarium care. In shallow water, typically on the tops of reefs, a "clonal form" occurs. Generally less than 2 inches in diameter (across the oral disc), this form occurs in large aggregations, with individuals often so close together as to give the appearance of a single anemone. In deep water, the polyps are of the "solitary form," and can be over a foot across. Fautin and Allen (1986) refer to the shallow-water form as the clonal form because the aggregations are thought to arise as a result of vegetative division of individuals, leading to a collection of genetically identical offspring — clones of the original anemone. The larger, deep-water form apparently does not divide in this fashion. (Heteractis magnifica shares this trait with Entacmaea.) Dunn (1981) points out that the relationship between size and type is not necessarily constant, with large specimens sometimes found in shallow water and small specimens occurring at greater depth (although any form of this anemone is rare below 60 feet).
Entacmaea is called the Maroon Anemone by some aquarium wholesalers because of its long-recognized association with the Maroon Clownfish, Premnas biaculeatus. Fautin and Allen report that this fish is found only in association with the deep-water, solitary form of the anemone, while the shal-low-water, clonal form is preferred by the Cinnamon or Bluestripe Clownfish, Amphiprion melanopus. A rare color variety, in which the body is red with pink tentacles, is called Rose Anemone by aquarium dealers and commands a high price.
Dunn speculates that in Entacmaea, the larger individuals are responsible for sexual reproduction (which makes sense when one remembers that a larger individual has more resources upon which to draw in order to carry out the demanding job of producing eggs and sperm). It is known that sexes are separate in Entacmaea, and the female anemones brood eggs, which are fertilized by sperm carried on the water currents. Despite the fact that the two different types may arise as a result of differing environmental conditions at different depths, it appears that the clonal form reproduces readily by asexual reproduction, whereas the solitary form does not.
Family Stichodactylidae. This anemone family is the more difficult one to manage in the reef aquarium. Heteractis aurora, Beaded Sea Anemone, is perhaps the easiest of this group to identify, as the tentacles are ribbed with swellings that are often a contrasting color. It hosts seven
clownfish species. H. crisp a, Leathery Sea Anemone, hosts pigment encircling the mouth. This species (despite the 11 clownfish species. It is sometimes confused with H. malu, use of gigantea as the species name for another carpet which Fautin and Allen (1986) call Delicate Sea Anemone, anemone) holds the oral disc size record for clownfish hosts but which in the aquarium trade is usually known as the Sebae or Singapore Sebae Anemone. H. malu hosts only it can be over 3 feet in diameter.
Clownfish host anemones in the Stichodactylidae fam-
Clark's Clownfish (Amphiprion clarkii), a species often in- ily have a mixed record of success in the aquarium, and the correctly identified as A. sebae. (The true A. sebae, a much majority of specimens probably die before reaching any-rarer species, associates in nature only with Stichodactyla thing approaching their natural lifespan. I know of one haddoni, discussed below.) H. crispa has a decidedly firmer specimen of H. malu that survived 12 years in a hobbyist's column than H. malu, but the latter is most easily recognized aquarium, but this seems to be an exception. It succumbed by the typically short tentacles, seldom over an inch in to loss of water quality during a prolonged power outage, length, that are tipped in magenta. H. magnifica, Magnifi- unfortunately, and barring this disaster might well be alive cent Sea Anemone, still goes by its old name of Radianthus ritteri in the aquarium industry, and is often called simply Ritteri Anemone. It is host to ten clownfish species, including ocellaris and A. percula, for which it is the most frequently suggested aquarium host.
Stichodactyla gigantea, the Giant Carpet Anemone of the aquarium trade, is host to seven clownfish species and can be separated from the other two Stichodactyla species by its noticeably longer tentacles, often strikingly colored. S. haddoni, Haddon's Sea Anemone, is called the Saddle Carpet in the aquarium trade, because of the affinity of the Saddleback Clownfish, A. polym-nus, for this host. The very short tentacles are frequently of two colors, giving the oral disc a mottled appearance and distinguishing this species from the other two carpet anemones. Be- Clark's Clownfish (Amphiprion clarkii) group, again with a clearly domi-sides A. polymnus, five other clownfish species as- nant female, in a Leathery Sea Anemone (Heteractis crispa). sociate with this anemone. Merten's Sea
Anemone, S. mertensii, is called Sri Lanka Carpet by aquar- today. The specimen more than doubled in size in a 55-ium dealers and is sometimes bright green in color. Its gallon tank. The tank was filtered with an undergravel fil-
stubby tentacles, often more like little knobs, are uniform ter and a canister filter containing activated carbon and was in color, although there may by a contrasting ring of purple illuminated with four 40-watt shop lights. Tank decor con-
208 Natural Reef Aquariums
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