Anemonefishes have long ranked as one of the most popular attractions for marine aquarists. Bright colours, interesting behaviour, and the ability to adapt to captivity are mainly responsible for their popularity. However, relatively few species of anemonefishes enter the aquarium trade, largely owing to the remoteness and lack of commercial collectors in areas where many of them occur. The False Clown (Amphiprion ocellaris) is the one most typically seen in pet shops; huge quantities are regularly shipped from the Philippines, Indonesia, Singapore, and Hong Kong. Also common are Clark's, Tomato, and Spine-cheek Anemonefishes (A. clarkii, A. frenatus, and Premnas biaculeatus, respectively).
Fish of at least a few species, on the other hand, are now raised in large quantities on commercial fish farms. Aquarists who purchase only captive-bred fish need not be concerned about decimating natural populations. Indeed, breeding anemonefishes offers a real challenge to the home aquarist. The main considerations for successful maintenance of anemonefish are provision of sufficient space, correct temperature, adequate filtration, proper water chemistry, ample shelter, and a nutritious diet. A number of excellent references available from pet stores, bookshops, and libraries adequately treat the subject of marine aquarium maintenance, which is therefore dealt with only briefly here.
Aquarium size There are no hard and fast rules, despite published formulas (often based on a certain amount of water per inch or cm of fish). Common sense should prevail above all else, and generally, the largest possible aquarium should be used. Smaller species, such as A. ocellaris and A. percula, or juveniles obviously require less space than do adults of species such as A. clarkii. Although Clown Anemonefishes (A. percula and A. ocellaris) have successfully spawned in tanks as small as 50 litres, one of at least 300 litres should be provided for a pair of adult A. clarkii or similar-sized fish.
Clownfishes, like other damselfishes, are often aggressive in community situations. Anemonefish of about equal size, particularly those of a single species, frequently fight when kept together, as do adults; smaller specimens are generally compatible with other reef fishes. Aggressiveness is usually enhanced by the presence of an anemone, as the host is regarded as exclusive territory by every fish. Advanced aquarists who wish to breed their pets should set up pairs in isolation, or at least avoid community tanks with larger species.
Temperature Temperatures existing in their natural habitat are recommended for the well-being of clownfishes in captivity. Most species occur in the tropics, where the water generally ranges from about 25 to 28oC. Subtropical species such as Amphiprion mccullochi and A. latezonatus can be maintained in slightly cooler water (22-25oC).
Filtration and water chemistry Filters on the market range from inexpensive subgravel types to sophisticated systems that monitor dissolved gas levels and cost more than $1,000. A few advanced aquarists, who usually live near the sea, utilise the so-called natural method, in which live corals and algae-covered rocks are maintained with little or no filtration. Regardless of filtration system used, a method of providing aeration and circulation (such as an airstone or bubbler) is essential. A minimal set-up for anemonefishes therefore must include a small electric air pump connected to a subgravel filter with a bubble tube and one or more airstones, depending on tank size. It is advisable to check nitrate levels and salinity occasionally, making necessary adjustments to achieve "normal" readings.
Diet In nature, anemonefish feed primarily on zooplankton (tiny animals, mainly crustaceans), supplemented with algae. This diet can easily be simulated, at least nutritionally, in captivity with finely chopped raw prawns and fish, and flake-type commercial fish food containing vegetable ingredients. This diet should be supplemented with live foods such as brine shrimp, Daphnia, mosquito larvae, and Tubifex worms whenever possible. However, freshwater organisms should be given in small quantities to prevent tank fouling. Several small feedings per day are better than a single one.
Shelter Shelter, in the form of rocks or small clay flower pots, is essential. If a rock shelter is provided, it is important to construct a small cave or crevice that can function as a retreat.
Anemones Captive fish can survive, and even breed, without anemones. Some clownfish adapt successfully to actinians from places such as Hawaii, California, the Caribbean, and the Mediterranean, but, for some, this means keeping the aquarium cooler than is optimal for the fish and warmer than is normal for the anemone. The natural hosts are occasionally collected, and sporadically offered for sale, but this practice is to be discouraged. Natural hosts do not survive well (see below), necessitating frequent replacement. Local populations of Amphiprion and Premnas have become extinct on some reefs in the Philippines because of wanton destruction of habitat with dynamite (often to get fish) and removal of anemones by commercial collectors.
Elimination of the already limited number of suitable hosts not only deprives fishes of their homes, but it means that there is no source of more anemones! Actinians are long-lived in nature (see Chapter 3). Moreover, we have never seen very small individuals of most species, so successful reproduction is probably rare for them. It therefore appears that these lovely animals are being harvested much more rapidly than they are able to produce replacements.
Ignorance about their reproductive biology, combined with difficulty in even maintaining them, preclude aquarium breeding of these actinians. In contrast to the fish, tropical sea anemones, including those with which clownfishes live, generally do not survive well under artificial conditions for reasons that are not entirely understood, but that probably have to do with nutrition. Most anemones lose their zooxanthellae after a short time in captivity. This phenomenon may be related to light, but the appropriate wavelengths and intensity are unknown, so the problem is difficult to remedy. It may also be related to the level of nitrogenous and other compounds in the water. Commercial aquaria that are successful at keeping corals (close kin of actinians that also possess zooxanthellae) circulate the water through beds of algae to remove such animal wastes, as happens in nature. This, of course, requires elaborate lighting and cooling. But even such enterprises generally end up with bleached anemones!
Lacking algae and probably a variety of natural nutrients, captive host anemones not only lose their normal colour, they assume shapes and postures not seen in nature. This can make them difficult to identify. For example, tentacles often shrink greatly, which probably means that the animal is living off its own tissues.
As mentioned previously, much useful information concerning the intricacies of the anemone and fish relationship has been gained through observation of captive specimens, particularly in large public aquaria. Even though we do not advocate the keeping of wild-caught tropical anemones, there is still much to be learned about the fishes. Amateur aquarists can certainly contribute to the growing fund of knowledge, particularly in the realm of clownfish reproduction, which has been adequately documented for relatively few species. Most serious aquarists maintain a logbook for recording notes on unusual and interesting behaviour. For those inclined to take this a step further there are a number of aquarium magazines that welcome contributions from the public. Even without these aspirations, the sheer enjoyment of keeping a tank of anemonefishes will not doubt ignite that same spark that Collingwood experienced on Fiery Cross Reef for than 120 years ago!