Depends on the species you wish to keep, but good general information be found with a quick search:
http://www.wetwebmedia.com/tridacnidart.htm">http://www.wetwebmedia.com/tridacnidart.htm</a>
[IMG]http://www.wetwebmedia.com/ca/volume_1/cav1i3/Clam_care/Clam_care.htm">http://www.wetwebmedia.com/ca/volume_1/cav1i3/Clam_care/Clam_care.htm</a>