Clown Triggerfish

With the large white spots on the lower half of its black body, the yellow net-patterned saddle on its back and its orange–yellow lips, the clown triggerfish is one of the most eye-catching fish in the marine aquarium. Stores sell juveniles of 5–8 cm; as an adult it becomes a 50 cm fish with powerful teeth and unpredictable aggression.

A fish that seems peaceful when young may, as it grows, one day kill even the tankmates it has lived with for years. For this reason it should only be considered for very large, fish-focused aquariums and with carefully chosen large companions. All individuals are collected from the wild.

It lives on open reef slopes of the Indo-Pacific, in clear water. Juveniles hide in deeper caves and under overhangs. It eats crabs, snails, sea urchins and other shelled creatures, crushing them with its powerful teeth.

• Volume: at least 1000 liters and 200 cm in length for an adult.
• Water: salinity 1.023–1.026 specific gravity, pH 8.1–8.4, temperature 24–27°C. As a large, messy eater, it needs strong filtration and a protein skimmer.
• Decor: secured rocks that cannot topple; place equipment and cables so they are protected from biting. Use a sturdy lid.
• Reef compatibility: not reef safe. It eats all invertebrates and any fish that fits in its mouth, and breaks corals.
• Maintenance: a 15–20% water change weekly; keep nitrate below 20 mg/l. When working in the aquarium, know where the fish is and keep your hands away from it.

Carnivorous. Shell-on shrimp, mussels, oysters, squid, krill, fish meat and large marine fish pellets. Shell-on foods wear down its teeth. Juveniles are fed twice a day, adults once a day; avoid overfeeding.

Intelligent and recognizes its keeper; but its temperament hardens with age and becomes unpredictable. It may attack its own species, other triggerfish and almost any fish; it can bite during hands-on maintenance, and its teeth cause serious wounds.

Good companions: in a very large aquarium, sturdy species of the same size or larger: large angelfish, large tangs, large puffers and porcupinefish, moray eels. Even so, there is no guarantee.

Avoid: small and medium-sized peaceful fish, all invertebrates, seahorses, slow-swimming species, an aquarium with corals.

Kept as a single individual in the aquarium, and it should be the last fish added.

In the wild, the pair lays its eggs in a nest dug in the sand and guards the nest fiercely. It does not breed in the aquarium.

• Hardiness: generally a robust species; still, a new fish should be watched in quarantine.
• Overgrown teeth: seen in fish fed only soft food.
• Bite wounds: the most common problem, both for other fish in the aquarium and for the keeper.

The sexes cannot be reliably told apart externally.