Chitons Can Be an Integral Part of a Reef Aquarium

Chitons are a group of mollusks that have been around for eons it seems, since the Cambrian Period to be exact. Their are roughly 900-1000 species of chiton that reside worldwide in both tropical or cold water regions. Most species of chiton make a welcome addition to a reef biotope due to their small size, unique build, often times brilliant coloration and their ability to forage for food in small places to help maintain clean live rock. Chitons rarely are offered for sale as a separate livestock though and are more accustomed to finding their way into your aquarium as hitchhikers on live rock and corals.

These mollusks are related to gastropods(snails) and bivalves(clams) and make up the class Polyplacophora. Unlike the chitons cousins, Chiton's are strictly marine whereas some bivalves and gastropods have adapted to brackish and fresh water as well. Chitons can be found in inter tidal zones all the way down to 20,000 feet in the deepest and darkest depths of the oceans. They range in size as well from a few centimeters to the large monster, the Gumboot Chiton of the Pacific Northwest that has been recorded at a whopping 33 centimeters!

Chitons are not too hard to distinguish and identify from other mollusks in the marine world. Getting around is provided by a muscular foot as they crawl along hard surfaces at a slow pace. They are able to attach themselves to surfaces like a snail and are hard to remove due to their strength of attachment. Their body structure and motion are similar to that of the Limpet (Chinese Hat). The distinguishing characteristic that separates these two mollusks is a Chiton has a shell that is comprised of eight calcareous valves or plates that are overlapping at the front and back end of the Chiton. These plates can articulate for turning purposes, plus Chiton's possess the ability to roll up in a ball similar to the terrestrial "potato bug" for protection. This shell and the eight plates are surrounded by a structure known simply as a girdle. The girdle of a Chiton can be smooth, spiked, have bristles, spicules, hairy tufts or be reminiscent of snake-like scales. These Chiton's can be very beautiful with bright colored patterns and shapes such as the Lined Chiton(Tonicella lineata) to a drab red to brownish color.

Having Chiton's in your aquarium is a good thing as most of these are harmless mollusks that will help to ensure that your live rock is free of algae, detritus, bryozoans, diatoms and bacteria. Finding these animals is the problem due to their small size and often hidden appearance in between live rock looking for a meal. Few of these are parasitic in nature, making them great additions to a reef aquarium as corals, and delicate sessile invertebrates don't have any worries. As for Chiton's falling prey to aquarium tank mates, their are not to many predators in a marine aquarium setting that consider the Chiton as a suitable food source. Octopus, Sea Otters, possibly a few crabs and Sea Stars and the Lurid Rocksnail represent the only real threat to the Chiton.

Chitons have the same body mold as bivalves. They have a shell, a mantle, gills, anus, mouth featuring a radula(magnetite-tipped teeth used for scrapping off food), incurrent and excurrent channels for water flow within its body cavity. The underside of a Chiton is reminiscent of a snail and when observed from above, or dorsally, all that can be seen of the soft tissue is the girdle while the snail-like foot and delicate organs and tissue are protected underneath their calcareous shell.

A fascinating, beneficial and sometimes beautiful addition to your marine aquarium. For the most part you may never see these in your tank, but be thankful, if you infact do, since these mollusks will be working overtime for you cleaning your live rock while helping to maintain a clean tank for you.