You are only after the mozzie larvae or daphnia if there is any in there. Don't put the algae in your tank!
How I harvest them is get a container and fill it with fresh water if you are going to feed out straight away, or tank water if you are going to keep them for a couple of days and feed them out slowly. Net the critters out and put them in the container. You do not want to be adding the water from the outside container to your tanks, and I feed them out with a turkey baster into the tanks.