Those look like cocco worms. Where did you get that kind of rock? Looks like it has lots of life on it, not like what we see around here. Those feather type worms feed on micro plankton, so DT's and similar is perfect. They'll like it when you run your magnets over the glass too or any fish go diggin things up a little. Nice find on those worms! They're expensive to buy when they are not hitchhikers.