To find out what is living in your pond you need to do some net sweeps. I may write a article about that in PB magazine when I get extra time. Sizes are in my post above. Most common ones will depend on your location and pond type. Without very many weeds or algae don't expect to find many. Most common one in western PA will probably be Hyalella azteca. Locations up near Lake Erie and Ontario could have G. fasciatus. I found G.fasciatus living among filamentous algae and overhanging grass in a local small ditch 1ft-3ft wide.
