
**Reef fish** is the collective term for the thousands of small and mid-sized fish species that live permanently on coral reefs — anthias, damselfish, butterflyfish, angelfish, wrasse, parrotfish, surgeonfish, fusiliers, snapper, groupers and countless others. On a healthy tropical reef they are the first thing you notice underwater: clouds of orange anthias hovering above the coral, parrotfish crunching on hard coral, butterflyfish patrolling in pairs and fusiliers streaming past the drop-off in silver rivers. Most reef fish spend their whole adult life within a few hundred metres of the same coral head, which is why they are so reliable to dive with. They are strictly tied to living coral: it gives them shelter from predators, hunting ground, cleaning stations and nursery habitat. Where coral cover is high, reef-fish density and colour are high too — which makes them the single best visual indicator of reef health on a dive. Behaviour changes through the day. Mornings and late afternoons bring feeding activity, hunting groupers and jacks pushing schools of fusiliers against the reef, while midday is the best time for slow macro-style observation of butterflyfish, angelfish and anemonefish. At dusk the day-active species disappear into the coral and the nocturnal shift — soldierfish, squirrelfish, bigeyes — takes over. For divers, reef fish are the reason a "normal" reef dive is never boring. Good buoyancy, a slow pace and a few minutes of hovering in one spot will show far more behaviour than swimming the reef end to end.
Size
Unknown
Weight
A few grams up to several kilograms; most classic reef fish stay under 2 kg.
Lifespan
3 to 20 years depending on family; small damselfish and anthias live a few years, large groupers and wrasse several decades.
Status
Not Evaluated
Many reef fish, including most wrasse and groupers, change sex during their life.
A single parrotfish can produce several hundred kilograms of white sand a year by grinding up coral.
Anemonefish are immune to the stinging cells of their host anemone thanks to a mucus coating.
Butterflyfish often live in lifelong pairs and patrol a fixed territory together.
A healthy reef can hold more than 500 fish species in an area the size of a football pitch.
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