The common clownfish is probably the single-most popular saltwater aquarium fish out there–ever. There is just some universal appeal about the bright orange color with white and black stripes that captivates the human mind.
saltwater fish image by Hilary Kladke
I know that was one of the first fish I had to have, and I suspect it may have been one of your first fish as well. If you’re like me, you probably also imagined yourself keeping the clownfish with a host anemone.
Do clownfish need anemones?
In the wild, clownfishes are found almost exclusively within reach of their host anemone (except when they are swimming out to touch the ‘butt’ like in Finding Nemo). In a home aquarium, clownfish do not need anemones and it is probably best if you don’t even try to keep them with an anemone.
Clownfishes generally take to aquarium life like a fish takes to water, but most species of anemone do quite poorly (and mostly die) in aquarium conditions.
According to a survey in Wilkerson’s book about Clownfish (admittedly dated), less than 1 in 18 anemones survived in captivity for 3 years and 1 in 36 made it to 5 years in captivity. To make a fantastic understatement, that’s pretty bad.
Why are anemones so difficult to keep? Anemones have very specific biological and environmental requirements that make them challenging for most aquarists. They are highly sensitive to water quality—elevated nitrates, ammonia, or even small fluctuations in parameters like salinity and temperature can cause stress or death. Anemones also require intense, stable lighting (often comparable to what is needed for demanding corals), moderate to strong water flow, and a mature, stable tank environment. Physical damage from handling or tankmates can be fatal, and many anemones are vulnerable to “chemical warfare” from other corals or invertebrates in mixed reef tanks. These requirements interact: for example, a sudden change in lighting or water chemistry can weaken an anemone, making it more susceptible to disease or injury. In contrast, clownfish are generally hardy and adaptable, tolerating a wider range of aquarium conditions than their natural hosts. This difference explains why clownfish thrive in captivity while most anemones struggle.
A great place to learn more about Clownfishes and their commensal relationship with anemones is the book, Clownfishes by Joyce D. Wilkerson (see Further Reading below).
The good news is that clownfish do not need a host anemone to be happy and healthy in your saltwater aquarium. They will do quite fine without one. If you’re lucky, they may even take up residence in a surrogate. The clownfish in my tank recently took up residence in a toadstool leather coral (Sarcophyton species) in the front of the tank. I have to admit, it’s a pretty cool sight to see.
Why do clownfish accept surrogate hosts? In the absence of a suitable anemone, clownfish sometimes adopt other corals or invertebrates as surrogate hosts. This behavioral flexibility is thought to be driven by their instinct to seek shelter and protection. Corals with large, fleshy polyps or soft, waving tentacles—such as toadstool leathers, frogspawn, or hammer corals—are sometimes chosen. However, not all clownfish will accept a surrogate, and not all corals tolerate the attention. Some corals may become stressed or damaged by repeated clownfish activity, while the clownfish may not receive the same level of protection as with a true anemone. If you want to encourage this behavior, provide suitable soft or large-polyp corals and observe interactions closely. If you wish to discourage it, avoid placing such corals in areas frequented by your clownfish.
If you MUST have an anemone…
If you MUST have an anemone, ask your local fish store for an aquacultured (if possible) bubble tip anemone. These anemones are hardier than the average anemone and look amazing. They are available in different shades of color that blend green and red.
Are you ready for an anemone? Before adding an anemone, consider the following:
- Tank maturity: Anemones require a stable, mature aquarium—generally at least 6-12 months old with consistently stable water parameters.
- Lighting and flow: Ensure your lighting and water movement meet the needs of the specific anemone species.
- Risks: Anemones are notorious for wandering around the tank, which can result in them stinging corals and other tank inhabitants, or even getting sucked into powerheads or overflows. This can cause significant damage or even tank crashes.
- Mitigation strategies: Use anemone guards or foam covers on powerheads, carefully plan placement away from sensitive corals, and allow the anemone to settle before adding new livestock nearby. Some aquarists temporarily restrict flow or use barriers to encourage initial attachment.
- If the anemone moves: If your anemone starts to wander, monitor it closely. Be prepared to move corals or invertebrates out of harm’s way, and check equipment regularly to prevent accidents. Sometimes, anemones move because they are unhappy with lighting, flow, or water quality—address these factors if wandering persists.
While bubble tip anemones are among the hardiest, all anemones require careful, ongoing attention. Weigh the risks and your tank’s readiness before making the leap.
Beware, though, that anemones have a bad habit of moving around your tank. You might be thinking…” yeah, so what?” The so what is that they can burn a hole of destruction along the way, stinging everything in reach and often end up sucked into a powerhead. I don’t mean to be so down on anemones, I just want to be real about all the challenges with keeping them healthy.
Why don’t clownfish get stung by anemones?
Apparently, the jury is still out on that question.
According to the AskNature.org website, clownfishes are protected by their mucous coat and get a little anemone mucus mixed in each time–eventually fooling the anemone into not detecting the clownfish at all.
According to wiki answers, the secret lies within the actual makeup of the mucus–and that clownfish lack the substance in ‘normal’ mucus that triggers the stinging response.
A third site reports that there is no consensus and that it could be either (or both).
What does this mean for aquarists? In captivity, clownfish and anemones may not always recognize each other immediately. When introducing a clownfish to a new anemone, there is a risk the fish could be stung if it rushes in before acclimating its mucus coat. Sometimes, clownfish never accept a particular anemone species, or vice versa, even if the pairing is common in the wild. To improve success, introduce the clownfish and anemone to a quiet tank, avoid sudden disturbances, and give them time to acclimate. Some aquarists use mesh barriers or acclimation boxes to allow gradual contact. Be patient, and understand that not all pairings will work—forcing the interaction can stress or injure both animals.
Personally, I think it’s because anemones have a good sense of humor. What do you think?
Further Reading
- Clownfishes by Joyce D. Wilkerson – an excellent resource on clownfish biology, breeding, and their relationship with anemones (may be out of print; look for used copies).
- AskNature.org: Clownfish protection from anemone stings
- WikiAnswers: Sea anemone adaptations