Just the one unknown species from the family Daphniidae. Water Fleas OR Daphnia are very common Crustaceans within ponds. The footage below taken down a stereomicroscope shows these tiny animals in detail…
The long tube is the gut, with the eyes located just beneath the antena and thoratic appendages which protrude from the head and help the Daphnia move about. Above the gut and just behind the head is the tiny heart and behind this towards the rear of the animal are three green embryos.
Wildlife Garden 