Among the diurnal species of the reefs two families are significant by their diversity. They are seldom observed by the divers because they are cryptic and of small size: gobies and blennies.

Gobiidae

These fish are seldom abundant on the reefs of atolls, but the gobies are sometimes the dominant fish on the soft bottoms where they live in burrows, their density being often much more significant than does let imagine the simple visual observation.

The great majority of these fish does not exceed a few centimetres, smallest vertebrate known belonging to this family, with adult fish of a size of 15 mm. The gobies present relatively varied ways of life, but in the atolls the majority of the species live on the bottoms. One observes species associated with burrows, living altogether with shrimps alphéides. It is about a kind of symbiosis, the shrimp ensuring the excavation and the maintenance of the burrow, the gobie ensuring the safety and bringing the most significant preys. These gobies often lives in pairs. The other gobies are in general without burrow and solitary. The food of the gobies includes especially tiny invertebrates, but many of the species are also planctophages. There is a specialized group (Gobiodon spp.) which is associated with the corals and which probably feeds on polyps.

Blenniidae

The blennies can be seen especially in the not very deep zones, even where the action of the waves is strong. Two great groups are distinguished: herbivora and carnivora.