black worms in pond waterfall

Question
Hello.  We have a lot of black worms about 3 to 4 mm long, they are anchored at one end, when put together they seem to form a ball or a line and stay together.  They are always in running water - we have a waterfall and there are so many they block up the holes.
Any idea what they may be?  The fish do not seem to be eating them.  We cant really tell, they seemed to eat them at first, but there are now so many of them the fish do not seem to be interested anymore.  
Thanks


Answer
They are probably blackfly larvae.  The fish can't reach most of them but you can rub them off into the water for the fish.  They are no harm to the pond.

Do they look like this:
http://www.fishpondinfo.com/insect2.htm#black

If they are smaller, they could also be caddisfly larvae ( http://www.fishpondinfo.com/insect.htm#caddis )

Good luck!

Robyn