There was a thread a few weeks back which I think called them flatworms,
mine have hair like legs down the sides like centipedes.

I've had them from the beginning, about 5 years, with no problems until they
got inside a clam which led to it's demise. I didn't know they were
responsible until I put the clam to dry out to at least recover the shell
and they all fell out.

If they are only in one rock, maybe a piece you just added to the tank and
there are no coral specimens on it etc., you could imerse it in fresh water
to get rid of the worms. Since mine are fairly widespread I pick off those I
can with tongs when I feed the fish and they come out.

Andy


"Ann R" wrote in message
news:bV%ve.1317$At6.745@trndny09...
I have a seething mass of reddish brown worms (at least I think they are
worms) in a piece of live rock down by the substrate. Today a piece of
shrimp floated down to it and the tentacles all wrapped around the shrimp
and pulled it in. A snail wandered over and the tentacles wrapped around
the snail. I have white spaghetti worms in my tank and they act nothing
like this mass. It looks nightmarish and acts predatory. The tentacles
actually wrap around its food and drag it. If you know what it is, please
tell me. If you know how to get rid of it, even better!!

--
Ann R