Saltwater Fish · Clownfish
Clarkii Clownfish
Amphiprion clarkii
The hardy yellowtail that hosts in anythingIntermediate
- Lifespan
- 10-15 years, sometimes longer
- Size
- 10-15 cm (4-6 in); female notably larger
- Social needs
- Solitary or one bonded pair only
- Time
- Daily feeding; weekly testing and water changes
- Cost
- Medium
- Diet
- Omnivore (marine pellets, meaty frozen, algae)
Overview
What is this animal?
- The Clarkii, or Clark's anemonefish, is the hardy middleweight of the clownfish family, with a dark brown-to-black body, two broad white bars, and bright yellow fins and tail.
- It has the widest natural range of any clownfish, from the Persian Gulf across the Indo-Pacific to southern Japan, and that adaptability shows in the aquarium.
- Females grow noticeably larger than males and can reach about 15 cm (6 in), a full size class above the Ocellaris.
- Its defining trait is anemone partnership: the Clarkii is the only clownfish recorded hosting in all ten natural host anemone species, so it is the species most likely to actually use an anemone in captivity.
- It does not need an anemone to thrive, and anemones themselves are demanding animals best left to experienced keepers with a mature system.
- Colours often darken with age, and captive-bred stock is widely available and worth insisting on.
- Choose a Clarkii as a step up from the beginner clownfish, at least as hardy as an Ocellaris but larger, more active, and more territorial.
- It is still a decade-plus commitment in a fully equipped marine system.
Temperament
- The Clarkii sits between the other clownfish in temperament, bolder and pushier than an Ocellaris but well short of a Maroon's outright aggression.
- Juveniles are peaceful, while a mature female becomes territorial, chases fish that stray into her patch, and may nip the hand that reaches in during maintenance.
- Like all clownfish they start life male, and the dominant fish of a pair changes sex to become the larger female.
- Keep one fish or one bonded pair, and never mix clownfish species in a single tank.
- They are reef-safe with corals, though a fish without an anemone may pester a coral by adopting it as a substitute host.
- Choose tankmates that can hold their own around a confident, fast-moving fish.
A good fit for
- Keepers stepping up from their first marine or reef setup
- Reef tanks that may add a hardy host anemone later
- Aquarists wanting the hardiest, most forgiving clownfish
- Tanks with open swimming room for an active, open-water fish
- Single-specimen or one bonded male-female pair setups
- Buyers who insist on captive-bred stock
Common mistakes to avoid
- Buying a host anemone before the tank is mature enough to keep one alive
- Mixing Clarkii with other clownfish species in one tank
- Underestimating a mature female's territorial temper at maintenance time
- An Ocellaris-sized tank for this larger, faster, more active fish
- No tight lid - clownfish are determined jumpers
- Skipping quarantine, which invites Brooklynella, velvet, and marine ich
Enclosure
Minimum 150 litres (40 US gallons)
Fine alone or with company. Solitary or one bonded pair only
- A bonded pair needs a cycled marine tank of at least 150 L (40 gal), and more is better, because this is a larger, faster swimmer than the Ocellaris that patrols open water rather than hugging one spot.
- The old 30 gal (115 L) figure is a bare minimum for a single fish; give a pair the extra length and swimming room.
- Provide live rock for territory and cover, plenty of open water, and a tight-fitting lid, since clownfish are determined jumpers.
- Maintain salinity 1.024-1.026, temperature 24-27°C (75-80°F), pH 8.1-8.4, ammonia and nitrite at zero, and nitrate below 20 ppm.
- Add fish only to a fully cycled system that has finished processing ammonia and nitrite.
- If you want the classic clownfish-in-anemone picture, a hardy bubble-tip anemone (Entacmaea quadricolor) is the usual partner, but it demands strong reef lighting, stable water chemistry, and a tank matured for six months or more.
- Treat the anemone as a separate advanced project, not a Clarkii accessory.
Supplies
Setup
- Tank, stand and sump
- Return pump and powerheads
- Protein skimmer
- Reef lighting
- Rock and sand
- Salt mix, refractometer and test kits
- Quarantine tank
Ongoing
- Quality small marine pellet
- Frozen mysis shrimp
- Frozen enriched brine shrimp
- Algae-based marine flake
- Vitamin or HUFA soaking supplement
- Small thawing cup and strainer
- Turkey baster for target-feeding
Safe substrate: Aragonite sand · Dry or cured live rock · Bare bottom
Care routine
Daily
- Check salinity, temperature and flow
- Feed small marine portions
- Head-count and look everyone over
- Top up evaporation with fresh water
Weekly
- Service the skimmer and filter socksevery 3 days
- Clean the glass
- Test the water
- Watch the pair's pecking order
Monthly
- Water changeevery 2 weeks
- Calibrate the refractometer
- Check salt, RO/DI and reagents
Less often
- Deep-clean pumps and powerheadsevery 3 months
- Replace RO/DI filter mediaevery 6 months
Vet: Quarterly review with a pair check — every 3 months
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.
YouTubers
HumbleFish & ReefSaltwater fish disease, quarantine and treatment (Humble.Fish forum)BRStvReef tank setup, fish health and quarantine series (run by a retailer)FishOfHex AquaticsBeginner saltwater guides, avoiding common mistakes and tank disasters
Sites
Go deeper
Diet
- Clarkii are unfussy omnivores with big appetites for their size.
- Feed a quality marine pellet as the staple, plus frozen mysis, brine shrimp, and finely chopped seafood, with algae- or spirulina-based food for balance.
- Offer small amounts once or twice daily, only what is eaten within a couple of minutes.
- They feed boldly and can outcompete shy tankmates, so make sure slower fish actually get their share.
- Captive-bred fish usually take prepared foods immediately.
- Vary the diet to keep colour strong, and remember that overfeeding is the fastest way to wreck marine water quality.
Health
- The Clarkii is arguably the toughest clownfish, but it shares the family's weaknesses: marine ich (Cryptocaryon), the fast-moving clownfish disease Brooklynella, and the even deadlier marine velvet (Amyloodinium).
- All three usually follow stress, poor water quality, or skipped quarantine.
- Quarantine every new arrival for several weeks in a separate tank before it joins the display.
- Watch for white spots, a greasy or peeling skin coat, scratching against rock, clamped fins, or rapid breathing, and act the day you see them.
- Stable salinity and temperature prevent most problems in this robust species.
- A healthy captive-bred Clarkii routinely lives 10-15 years, and sometimes longer, so plan for the commitment, not just the purchase.
Is your enclosure big enough?
Minimum volume150 litres (40 US gallons)
CompanyFine alone or with company. Solitary or one bonded pair only
Is this urgent?
In a reef, stability matters more than any single target number. A parameter moving fast does more damage than a parameter sitting slightly off.
Go now
Any detectable ammonia or nitriteWater change now with matched, mixed and aerated saltwater. Stop feeding. Directly toxic, and a marine system has less margin than a freshwater one.
NowTemperature or salinity has moved sharplyCorrect slowly, over hours, not minutes. Check the heater and the top-off. The speed of the change does the damage. Correcting fast repeats the injury in the other direction.
NowRapid gilling, or a fish hanging in the flow breathing hardIncrease aeration and check temperature and salinity. Warm water holds less oxygen, and a heater failure shows up here first.
NowToday
White spots, or a fine dusting like icing sugarIdentify which parasite before treating. Most reef tanks cannot be treated in place. The two common parasites look similar and need different handling; velvet can kill a tank in days.
TodayCorals closed for more than a day, or receding tissueTest alkalinity first, and compare it against the last reading rather than a target. Unstable alkalinity is the most commonly cited coral killer, and a swing shows up in the trend, never in a single point.
TodayA new fish added without quarantine now looks unwellRemove it to a separate system today if you can. Nearly every wipeout in a reef tank traces back to a skipped quarantine.
TodayQuarantine every new animal, including corals and inverts. It is the single practice that separates a reef that lasts from a reef that restarts.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Bedding and substrate
In a marine system the rock and the sand are life support, and how you start them decides the first six months.
Safe
Aragonite sandThe standard marine substrate. Buffers pH and hosts the biology.
safeDry or cured live rockDry rock avoids importing pests but takes longer to mature. Cured rock is faster and riskier.
safeBare bottomCommon in high-flow systems. Easier to keep clean, but it removes a large part of the biological buffer.
safeWith a caveat
Deep sand bedsPowerful nutrient processing when they work and a sulphide release when they are disturbed. Choose shallow or deep deliberately, not by accident.
with a caveatUncured live rockIt will cycle the tank for you, and it will also bring in whatever was living in it.
with a caveatNever
Silica play sandDoes not buffer, and it is commonly blamed for feeding diatom blooms in a new tank.
neverAny rock or decor of unknown originMetals and phosphate leach for months and are almost impossible to trace once the tank is running.
neverThis is our general list for saltwater fish. We have not built one specific to Clownfish yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
Keep going
Clownfish, side by side
Same axes, same care guides — the honest way to choose between types.
See all Clownfish side by side →
