Hello Bob,
it is a copepod, a small freshwater crustacean. This is the most abundant zooplancton species in the mixure that I get harvesting a big pond. I'm using it as live food for the fry.
Last year I had a rather important mortality of fry when I started using Artemia. It was caused by Artemia egg shells and unhatchet eggs being eated by the fry. They can't digest the shell and die. It is difficult to extract just the nauplius from Artemia cultures. This year I want to decapsulate the Artemia eggs to overcome this problem. The chemical procedure is not difficult and have many advantages:
http://www.fao.org/DOCREP/003/W3732E...0.htm#Contents
involves using sodium hypoclorite (bleach) and later sodium tiosulfate to neutralize the clorine. I'm still waiting for the sodium tiosulfate that ordered one week ago. In the meantime, I must stick to my live food cultures plus copepods and some daphnia harvested from the pond.
Diego