These guys are kinda all over the tank. They don't seem to be doing anything wrong, not sure if they are filter feeders or what. They look attached to the rock at one end and flail around until something touches them. I've seen them bump into the rock and grab on, they then let go (tail still attached) and will shrink a bit before expanding out to flail around in the flow.
They're about an inch long and only seem to attach to non-glass hard surfaces like my rocks.
They're about an inch long and only seem to attach to non-glass hard surfaces like my rocks.