We have tiny redish worm like insects in our unopened pool, how do we get rid of them and are they harmful?

We are cleaning out our pool that has alot of algae in it, i came across theese VERY tiny worm things that swim very fast ( they sliver like a snake) i did some research and it seems that they might be some sort of larvae that contain hemoglobin. How do i get rid of them but most importantly are they harmful?!