Species of Caulerpa occupy in the Red Sea a very wide range of habitats as compared to any other single genus. They appear from the partly exposed belts of intertidal zone down to the greatest depths from which benthic algae were obtained in the Red Sea, i.e. ca., 120 m. While an important group of species - those which are more robust-such as C.racemosa or C. serrulata, prefer soft substrate and are almost exclusive in sandy or muddy bottoms, the delicate species such as C. webbiana or C. peltata are exclusively found in rocky habitats or in coral reefs. A third group of species, such as C. mexicana may be found on both crumbly and firm substrates.

Morphological variations occur between populations of the same species which grow in different habitats, while parallel characteristics appear in variants of different species growing in the same habitats.