Clarkii Clownfish

Overview

• 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.

Housing

• 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.

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.

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.