Here are a couple of introductory, non-technical pages on ostracods: http://www.ucmp.berkeley.edu/arthropoda/crustacea/maxillopoda/ostracoda.html http://www.arctic.uoguelph.ca/cpl/organisms/inverts/marine_inverts/ostracods .htm Though vernacular names have no official standing, the name "water flea", in my experience, most often refers to free-swimming cladoceran crustaceans like Daphnia sp. The common name for ostracods that I am most familiar with is "seed shrimp". Regards, Paul M.