Clownfish
It lives in an anemone that would sting anything else, protected by its own mucus. Every clownfish starts male, and the dominant one of a pair turns female.
Overview
The clown anemonefish reaches about 11 cm and lives in shallow, calm lagoons on Indo Pacific reefs, tucked into a host anemone. FishBase names three hosts it associates with: Heteractis magnifica, Stichodactyla gigantea and Stichodactyla mertensii.
It is also one of the few marine aquarium fish that is genuinely farmed rather than caught, bred artificially in Florida for the trade. A captive bred clownfish takes to a tank far more easily than a wild caught one, and it is the reason this species is the usual first fish in a marine setup.
Temperament
Bold for its size and strongly tied to one spot. A pair is monogamous, and the male guards and aerates the eggs.
Every clownfish starts male. They are protandrous hermaphrodites, and in a pair the larger fish becomes female, with the change happening around 4.4 cm. Two juveniles put in a tank together will sort this out between them. Adding a third adult later usually does not work, because the pair already exists and the newcomer has no place in it.
Care and grooming
Marine flake, frozen food and small prey, fed twice a day.
The work in a clownfish tank is salinity and stability rather than the fish itself. Reef parameters, around 74 to 80 F and pH 8.1 to 8.4, held steady. An anemone is optional: clownfish live and breed in bare tanks without one, and an anemone has lighting and water quality demands considerably harder than the fish does, so it is a second project rather than part of the first.
Living and exercise
Twenty gallons of marine water suits a pair. They use very little of a tank, staying near whatever they have adopted as home, which may be an anemone, a coral, or a corner of the glass.
Other fish are mostly ignored unless they approach that spot. Two clownfish of the same species that are not a bonded pair will fight, so the reliable arrangement is a pair bought young together, or one fish on its own.
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