I don't know what they are, but I put what I vacuumed out of my pool in a tuperware container. They are growing longer! They seemed to be dead when I got them out of the pool, but are now moving and growing. The chlorine level in my pool is pretty high and doesn't seem to bother them. I don't think they are springtail. I would like to know what they are. Does anyone else with these have mature trees near?