PomacentridaePomacentridae

Some damselfish are farmers, and they mean it. A gregory or a jewel damsel holds a patch of dead coral rock about a meter across, and it does not simply feed there, it weeds: the algae it does not want are bitten off and carried out of the plot, and the ones it does want are left to grow into a dense turf. In some gardens the crop is a red alga that is now found almost nowhere except inside them, kept going by the fish that eats it. Where the plot needs to be bigger, the farmer kills coral to make room, biting the polyps off in a line along the edge until the bare skeleton is ready for turf to move in.

Then it defends the whole thing against everything: other damselfish, wrasses, a mob of surgeonfish passing through, and you. Being charged in the mask by a brown fish the length of your finger is a standard 🌊 Red Sea experience, and the fish is not confused about what it is doing. It is defending a food supply that took it months to build, against an animal a thousand times its size, and it usually wins, because you move on.

The other half of the family points the opposite way. Chromis hang in clouds above the coral heads, facing into the current and picking plankton out of it one item at a time, then drop into the branches at dusk; between them they work as a conveyor, moving open-water food onto the reef and leaving it there. Farmer and plankton-picker share one small oddity: a damselfish has a single nostril on each side of the snout, where nearly every other bony fish has two.

Thirty-five species are listed here, which makes them the most numerous fish on a 🌊 Red Sea reef and the ones divers look at least. The anemonefishes belong to this family too, and are covered separately.