Clownfish / Anemone Fish
Amphiprion

It is fair to say that many marine aquarists are initially attracted to the hobby by the prospect of keeping a clownfish or two and a host anemone in order to witness this wonderful example of symbiosis. The sight of a clownfish nestling in its anemone is extremely beguiling but in practise it can prove a frustrating thing to achieve.

Why might this be the case? It is widely believed that the ability of clownfish to occupy the tentacles of anemones without stimulating the invertebrates stinging response rests, to some extent at least, in the production of a special mucous by the fish which inhibits the firing of the anemones stinging cells.

Some authors believe that fish that are acclimatised to one particular anemone species may not be physically capable of acclimating to another, at least not in the short term. Whether this is true or not juvenile clownfish demonstrate specific preferences when they seek out a host anemone for the first time.

Another problem for the aquarist lies in the apparent loss of whatever protection may be present after a clownfish has been in the aquarium for some months. However, these problems also seem to be overcome by many clownfish individuals and a little patience coupled with a little knowledge of the preferences of wild clownfish can prove essential in success with anemones and their occupants.

It is a commonly asked question. What anemone should I buy for my clownfish? Unfortunately the answer is far from simple but in my opinion the best way to consider this question is to look at the preferred wild host anemones of clownfish and then choose the hardiest of these species for our aquaria. (Note: I am aware that strict terminology dictates that I only refer to two of the many species as clownfish and the others as anemone fish but to avoid unnecessary confusion I will consider all species as clownfish.) As this article considers various species of clownfish and the ten species of anemone known to host them in the natural world I have compiled two tables based on anemones and their hardiness and the wild host anemone species for a representative sample of commonly kept clownfish species. Please refer to these as you read this article.

There are twenty-eight recognised species of clownfish found throughout the tropical and sub-tropical Indo-Pacific region. Of these only one species in not a member of the genus Amphiprion and that is the maroon clownfish, Premnas biaculeatus. A hardy and beautiful species the maroon clownfish is actually the easiest to find a host anemone for. Wild specimens only occupy the bubble or gelam anemone (Entacmea quadricolor) and if you want an anemone for your fish then this is it. Such is the desire for a host of the maroon clownfish that I have seen individuals get into a bag containing an acclimatising anemone! I am confident that a maroon clownfish given a bubble anemone as a host will occupy it within a matter of minutes in the vast majority of cases. However, other anemones will also be occupied including the “Ritteri” anemone (Heteractis magnifica), sand anemone (Macrodactyla doreensis) and sometimes the leathery anemone,( Heteractis crispa).

Unfortunately, the maroon seems to be the exception rather than the rule. Amphiprion spp. clownfish can prove extremely finicky about the anemones they choose to occupy. Part of the problem is due to the incorrect identification of anemone species. For example, there are two species commonly sold as “malu” anemones; the true malu, Heteractis malu and the leathery anemone, Heteractis crispa. Superficially they are quite similar and are often available with almost identical colouration but malus have short tentacles ending in a rounded tip and H.crispa has long tapering tentacles ending in a pointed tip. It may seem that I am being pedantic about this matter but when you consider that many of the clownfish species commonly sold by U.K. dealers will occupy one or the other but not either in the wild the distinction between the two becomes relevant. One exception to this is Clark’s clownfish. Amphiprion clarkii is the only species of clownfish that is known to occupy all ten of the host anemone species in the wild. This is good news for the aquarist as all they have to do therefore is choose their host anemone specimen and the Clark’s clownfish will occupy, albeit after a possible delay.

Incorrect identification of clownfish species can also be a problem. Take the two often-confused favourites for example, the common clownfish, A.ocellaris and the percula, A.percula. Wild specimens of A.ocellaris are known to frequent the “ritteri” anemone (H.magnifica), and two species of carpet anemone Stichodactyla gigantea and Stichodactyla mertensii. However, the percula can also occupy H.crispa. I have found that H.crispa is the better anemone to keep as it seems to be much hardier than H.magnifica and less problematic than the carpet anemones.

There is also the difference in individual fish to consider. It is all very well to explain the wild preferences of clownfish but there will always be certain specimens that defy the best attempts to provide a host anemone. Tank raised clownfish have often been cited as reluctant to occupy an anemone and to a certain extent this may be true. Certainly many specimens will never have experienced an anemone before taking residence in an aquarist’s aquarium. However, I have seen small captive bred common clownfish of no more than 10mm in length go straight into an anemone without hesitation. Subsequent enquiry revealed that these individuals had been bred by a hobbyist who introduced them to an anemone as soon as they had undergone metamorphosis. Given enough time (as much as six months) even larger tank raised specimens will eventually adopt an anemone but a reluctance to do so may indicate that one of the aforementioned factors maybe to blame.

Table 1
The ten species of anemone that play host to clownfish. I have included a “hardiness index” based on my own and others experiences with these anemones in aquaria. The higher the number the more difficult this species is to keep. Note that many species share similar or identical common names.

Table 1

Table 2
This Table shows a number of commonly kept clownfish species and the anemones which play host to them in their natural environment. This can be used as a guide for anemone selection but it must be stated that some clownfish will use almost anything as an anemone whereas others, even given their preferred host anemone, will show great reluctance to take residence.

Table 2

Some species of clownfish, for example the Red Sea clownfish, may be the only one resident in a particular region and so it will be to it’s benefit to be able to occupy all of the available host anemones in the area. Other species may share their reef with several other clownfish species in which case some host specificity is required although some species retain the ability to take whatever is available. An interesting thing to consider here is that the juveniles of several clownfish species use the beaded anemone (Heteractis aurora) as a host. These attractive anemones are relatively hardy but their small size means that they will offer little protection to large individuals and so few species occupy them when adult. In the aquarium situation large clownfish will often still try to get into these anemones damaging them at worst or at best preventing them from settling.

Another word of caution must be made concerning the magnificent anemone (Heteractis magnifica). You will notice from Table 2 that 11 of the 16 species listed will accept this anemone as a host. This is undoubtedly one of the most attractive species of host anemone with some stunning colour varieties available. However, in most cases this anemone does not prove hardy in the aquarium despite the aquarist’s best attempts. It requires excellent water quality but above this many seem to require the intensity and colour spectrum of lighting that we do not tend to light our aquaria with. I have seen some specimens grow to almost 75cm in diameter under 4200 Kelvin metal halide lighting, yet never settle under 10,000 or 13,000 K. This is simply an observation and may be coincidental but the bottom line must remain that this species is best avoided by all but the most experienced.

I hope that the two Tables shown here will assist those of you who would like to pair a clownfish with an anemone. Please remember that clownfish can exist quite happily without a host and careful consideration should be given before acquiring any of the species listed in the Table 1. Anemones require careful selection and subsequent husbandry. Don’t be in a hurry to purchase one. Studies have shown that mortality rates of anemones are over 40% in the first three months when acquired by aquarists with less than six months experience. Take your time, hone your skills and select an anemone that has settled well at your dealers. Although they are no guarantee for success sensible practises like these will help you find the right anemone for your clownfish.

References:
Delbeek & Sprung, 1997. Reef Aquarium Volumes 1 & 2. Ricordea Publishing
Fossa & Nilsen. The Modern Coral Reef Aquarium Volumes 1,2 &3. BSV Publications
Lieske & Myers, 1994. Coral Reef Fishes. Indo-Pacific and Caribbean.. Harper Collins Publishers
Wilkerson. Joyce D. 1998. Clownfishes. Microcosm Ltd