Caulerpa taxifolia is a species of seawee (a type of algae), native to the Indian Ocean, that has been commonly used as ornamentation in aquarium installations around the world. The algae has a stem which spreads horizontally just above the seafloor, and out of this stem there grow vertical fern-like pinnae, whose blades are flat like yew, hence the species name "taxifolia" (the genus of yew is "taxus"). The algae produces a large amount of a single chemical that is toxic to fish and other would-be predators. This is in contrast to other plants which produce a variety of toxins, but in reduced amounts.