Planaria are white, somewhat smaller than described, and will usually be
seen on the glass after lights-out.

coelacanth wrote in message
. com...
I think these are probably planaria or other flatworm. They live
on excess food and are usually harmless (though they have near
relatives which are parasitic and not usually seen in a free
swimming stage). Try feeding a little less if they get out of hand.
Many fish relish them, so they may just disappear.

They may have come to you on a plant or unnoticed in the
bag with a fish.

-coelacanth

"Jim K" wrote in message
...
I need some help identifying worms in my aquarium. My tank is heavily
planted, and I recently found some worms moving along the substrate.
They
are reddish-brown, about 2 inches in length and 1/8" in diameter. I
would
supply a photo but they disappear very quickly.

My questions a

1. What are they?
2. Where would they have come from?
3. Are they harmful to the fish?

Thanks in advance.