Saltwater Fish · Clownfish

Clarkii Clownfish

Amphiprion clarkii

The hardy yellowtail that hosts in anythingIntermediate

Lifespan: 10-15 years, sometimes longer
Size: 4-6 in; female notably larger
Social needs: Solitary or one bonded pair only
Time: Daily feeding; weekly testing and water changes
Cost: High
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 6 in, a full size class above the Ocellaris.

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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.

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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
A short 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 79 gallons

Fine alone or with company. Solitary or one bonded pair only

A bonded pair needs a cycled marine tank of at least 80 gal that measures at least 3 ft from end to end, and more is better, because this is a larger, faster swimmer than the Ocellaris that patrols open water rather than hugging one spot.
Retail care cards quote 30 gal, but a lone Clarkii needs the same tank as a pair, because it is the swimming length that sets the size, not the number of fish.
Provide live rock for territory and cover, plenty of open water, and a tight-fitting lid, since clownfish are determined jumpers.

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Maintain salinity 1.024-1.026, temperature 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.

Check your enclosure

Supplies

Setup

Tank, stand and sump, about 80-90 US gallons
Return pump and powerheads
Protein skimmer
Reef lighting
Rock and sand

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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

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Small thawing cup and strainer
Turkey baster for target-feeding

Safe substrate: Aragonite sand · Dry or cured live rock

Work out the cost

Care routine

Daily

Check salinity, temperature and flow
Feed small marine portions
Head-count and look everyone over
Top up evaporation with fresh water

Every few days

Service the skimmer and filter socksevery 3 days

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Weekly

Clean the glass
Test the water
Watch the pair's pecking order
Water change

Monthly

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

Health review: Quarterly review with a pair check, every 3 months

Tools

Is your enclosure big enough?Check your measurements against the recommended size What will it cost?Setup, monthly and over its whole life, itemised Is this ammonia reading dangerous?Works out the toxic part from your pH and temperature

Care in depth

Diet

Omnivore (marine pellets, meaty frozen, algae)

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

Signs of good health, and the common problems

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 this urgent?

6 warning signs and how fast to act, 3 of them right away

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. Ammonia is directly toxic, and at reef pH more of it is in the toxic form, so a marine system has less margin than a freshwater one. Nitrite is far less toxic in seawater, but any reading in a stocked tank means the biological filter is not keeping up.

Now

Temperature 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.

Now

Rapid 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.

Now

Today

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.

Today

Corals 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.

Today

A 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.

Today

Quarantine 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.

Bedding and substrate

2 safe, 3 with a caveat, 2 to avoid

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, and it hosts the biology. It does not meaningfully hold pH or alkalinity at normal reef pH, so test and dose for those regardless.

safe

Dry or cured live rockDry rock avoids importing pests but takes longer to mature. Cured rock is faster and riskier.

safe

With 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. A sand-sifting or burrowing goby needs a fine bed about 2 to 3 in deep that it turns over itself. That is a different thing from a denitrifying deep sand bed (4 in or more, left undisturbed), and the two do not mix: a sifting goby disturbs the layers a deep sand bed depends on and eats the life in it.

with a caveat

Uncured live rockIt will cycle the tank for you, and it will also bring in whatever was living in it.

with a caveat

Bare bottomWorkable in high-flow systems for fish that neither sift nor burrow, but it removes a large part of the biological buffer. Wrong for watchman gobies and other gobies that burrow or sift, which need a fine sand bed at least 2 in deep to dig and feed in, and for mandarins and other copepod-eaters, which need sand as well as mature rock for their food to breed in.

with a caveat

Never

Silica play sandNot the marine standard, and commonly blamed for feeding diatom blooms in a new tank.

never

Any rock or decor of unknown originMetals and phosphate leach for months and are almost impossible to trace once the tank is running.

never

This is our general list for saltwater fish. We have not built one specific to Clownfish yet.

Top resources for more info

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