Echinoidea (Sea urchins)

Sea urchins are often used to keep various algae at bay. 

They are very effective algae eaters, and will eat anything from coralline algae to green hair algae.
Sea urchins must not be kept in an aquarium with few algae, as they may starve to death. 

Sea urchins should be acclimatized slowly, due to sensitivity towards changes in salinity.

Asthenosoma

Diadema

Echinothrix

Heterocentrotus

Mespilia

Tripneustes