These are so named because they set up cleaning stations and offer to pick parasites off of fish, even from within the mouths of the larger fish (which cooperate). Their coloring is beautiful, with orange, bright white, and deep red; the pattern on the back and tail is characteristic. If you stick your hands into the tank, they often will come running over and try to clean bits of loose flesh from off of your hand. They can pull surprisingly hard for such a small creature.
Still has lots of feet up front! Notice that one pair is white, rather than brownish orange.
Here is a camel shrimp (lower left) and a cleaner shrimp (upper right). A rittori anemone can be seen in the upper left; a bit of a flower pot coral in the lower left; and a small colony of yellow fiji polyps on the right.
A tongue coral can be seen in the right background, with a small colt coral way in the background at the left.