Ostradcods are a common crustacean, sometime also known as seed shrimp. Like their names imply, they are very small. Their typical size ranges from 0.2 mm to 30mm. Seed shrimps are protected by a bivalve-like shell. The hinge of the two valves are fused on the top of dorsal region of the body.
While looking into the recent pond water sample, I can clearly see some little creature clinging to the side of the container occasionally jumped and swam like copepods. Curiously about what this is, I syphon one of this little creature and place it on a 96 well plate. It looks like a clam but some tentacle and appendages coming out of the shell. With the help from the friends from yahoo amateur_microscope group (http://groups.yahoo.com/group/Amateur_Microscopy/message/4713) . It is identified as ostracod.