Clownfish and sea anemones have a symbiotic, mutualistic relationship; each providing a number of things to benefit the other. The individual species are generally highly host specific, and especially the genera Heteractis and Stichodactyla, and the species Entacmaea quadricolor are frequent clownfish partners. The sea anemone protects the clownfish from predators, as well as providing food through the scraps left from the anemone's meals. In return, the clownfish defends the anemone from its predators, and cleans it from parasites. The anemone also potentially picks up nutrients from the Clownfish's excrement, and functions as a safe nest site. It has been theorized that the clownfish use their bright colouring to lure small fish to the anemone, and that the activity of the clownfish results in greater water circulation around the sea anemone.
Clownfish and certain damselfish are the only species of fishes that can avoid the potent poison of a sea anemone.