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Author: Leslie Tsen (B.S.) Ecology, Evolution & Natural Resources. Wildlife Conservation
Clownfish is a generic name for at least 30 species of anemonefish that are known for their symbiotic relationship with sea anemones. Most recognized clownfish are found under the genus Amphiprion (at least 29 species) while only one recognized species has been found under the genus Premnas as Premnas biaculeatus. Amphiprion and Premnas are sister genera to all other damselfishes’ genera under the Pomacentridae family. This indicates that damselfish and clownfish are evolutionarily very closely related to one another. Clownfish are one of the most commonly encountered inhabitants in coral reef aquaria due to their attractive coloration and unique personality. Owing to their hardiness and adaptibility, clownfish are often recommended for newbie aquarists who have just started in the marine fishkeeping hobby. A more conservative estimate on clownfish’s life expectancy is around 6 to 10 years, but there have been multiple reports on captively reared clownfish living up to 20+ years.
When discussing about clownfish, it is almost impossible to neglect their anemone hosts as these are their natural home much like how bears choose to live in dens, bees construct hives, and bats find shelter in caves as well as tree holes. Technically speaking, anemones are animals. They are equipped with stinging cells for both prey capturing and defensive purposes just like all other cnidarians such as corals and jellyfish. One of the major differences between an anemone and a coral is that all corals are obligatively sessile while anemones are facultatively sessile, having the capability to move around if the living environment is unfavorable. Another major difference between an anemone and a soft body coral is that coral secrets calcium carbonate to strengthen its skeleton, while anemones are entirely fleshy. In order to stay anchored, anemones held on to hard surfaces using their pedal disc.
All clownfish exhibit a highly host-specific symbiotic mutualism with their anemone hosts. Distinct species of clownfish rely heavily on specific host anemone species to protect them from predators. In return, they clean their host anemone from algae and invertebrate parasites as well as providing food scraps and nitrogen-rich fecal matter for nourishments. Perhaps one of the most commonly observed behavior in clownfish is the act of rubbing against their host anemone yet still being able to survive the lethal stings. Just exactly how these small-bodied clownfish are immuned to anemone’s venom when it is so deadly even for larger fish has baffled biologists even to this day. Several scientific studies have suggested that clownfish acquire their venom immunity through three primary means – innate, acquired and a combination of both. Some clownfish are innately born with the immunity to their host anemone’s venom while some acquire such immunity by coating their slime coat with the antigen from their host anemone’s venom. In some other cases, both methods of immunity are applied. When housing clownfish in home aquaria, be sure to house the correct host anemones species to their corresponding guest clownfish as incompatibility will result in fatal consequences.
Most if not all Amphiprion clownfish species live in small social circles containing up to several individuals. The social structure of clownfish is a rather interesting topic. Smaller clownfish are usually sexually immature males while the largest, most dominant individual is often the female in both social groups and in mated pairs. The second largest individual in a social group will always be a male who gets to mate with the dominant female. Should the dominant female died, the second largest individual (male) will instinctually and physiologically replace her by switching gender. One smaller male will then be able to move up the social rank by occupying the mating male’s position.
Individuals use sound to establish social structure. Beside the usual charging and chasing behaviors, dominant individuals are also known to produce a distinct popping sound by repetitively clenching their teeth when exerting dominance over their subordinates. To avoid getting injuries, submissive individuals often produce a static noise through continual head shaking and lateral body quivering to signal that they are in no mood for a fight.
While parental care is common among most clownfish species, the typical gender roles are often time reversed. Females are usually the one protecting their family by actively patrolling around the nest to ward off intruders while males assumed their paternal duty as caregivers by spending the majority of the time taking care of their eggs. Aside from benefiting from mom's protection, these eggs have also been shown to improve in overall hatching success from dad’s repetitive fanning and mouthing actions. Fanning aerates the surrounding water to improve oxygen flow in dead spots while mouthing significantly reduces parasites and algae growth as well as preventing dead eggs accumulation that might otherwise spoil the entire egg clutches.
Clownfish are opportunistic omnivores feeding on a wide variety of food items. In the wild, they feed on algae as well as small invertebrates such as molluscs, crustaceans, worms, and planktons. They rid their host anemones off algae that might otherwise suffocate them if left unchecked, and nip off pesky parasites such as amphipod and isopod that might otherwise inflict serious damages to their hosts’ delicate tentacles. In household aquaria, clownfish will readily accept many type of fish food be it live foods, flakes or pellets. Ideally, your clownfish should be fed with high quality foods that are primarily formulated with both vegetative and animal materials such as algae, Spirulina, kelp, seaweed, phyto- and zooplankton, fishmeal, shrimp, and mollusc. Try to avoid fish food that has been added with too many fillers such as corn and soy.
There are several interspecies (between different species) interactions that need to be considered when housing clownfish in a community tank. In general, clownfish can be safely added into most community tanks as long as their host anemones are also included. However, be wary that certain species of anemones (eg: rose anemone) are capable of killing many non-guest species. It will be best to conduct a thorough background research and plan accordingly prior to purchasing one for your aquarium. If you have to, use a large divider to separate out the clownfish-anemone pair with the rest of the fish so that any “accidental” death can be avoided.
We also mentioned earlier on that clownfish are highly host specific, and that not all species of anemones are suitable host. There have been multiple documented cases of anemones killing and eating clownfish due to incompatibility between the two. For example, the fish-eating anemone, Urticina piscivora will not house clownfish, but it will house Painted Greenling, Oxylebius pictus and candy-striped shrimp, Lebbeus grandimanus. There are about 30 recognized clownfish species with each having its own unique host anemones. Despite so, it is not uncommon to find host anemones species that are utilizable by multiple clownfish species. For instance, the Merten’s carpet anemone (Stichodactyla mertensii) is used by many clownfish species including but not limited to orange-fin anemonefish (Amphiprion chrysopterus), orange skunk clownfish (A. sandaracinos), false percula clownfish (A. ocellaris), and yellowtail clownfish (A. clarkii). Different species of clownfish have also been observed to dwell peacefully within the same anemone individual. In household aquaria, different clownfish species can be allowed in the same tank as long as they share a common anemone host, do not exhibit life-threatening aggression towards one other, and are not bothered by the establishment of social hierarchy.
Although organisms such as sea crabs, marine hermit crab, sea slugs (nudibranch), and butterflyfish will generally do fine with clownfish, they are also anemone eaters known for their unique appetite to nom on clownfish’s home. Therefore, we do not recommend housing these with your clownfish-anemone pair. The ideal water salinity for this most clownfish is 33-35ppt with a water specific gravity of 1.020-1.026, water pH 8.0-8.4, and a water temperature of 24-28°C.
Disclaimer: This article contains materials referred from published scientific journals and is strictly meant for educational purposes only. It must NOT be substituted for any forms of medical care, treatment, and consultation from veterinarians, aquatic experts or other licensed professionals. NO compensation shall be reimbursed by Harvest Fish & Pet for the direct or indirect loss, damage, injury, or death of both living (user included) and non-living beings caused by the application of information from this article either in full or in part.