worms in pond

Question
My babysitter has a small ornamental pond at her house.  When she cleaned it this spring she found tons of small string like worms that wiggle around a lot.  They had eaten all the roots from the plants and were really thick on the pond bottom.  She has some frogs, water plants, and just added a few fish to the pond.  She's worried about what they are, the health risks to the children and animals, and how to get rid of them.  I haven't been able to find much about them on the internet.  Can you please help our worries?

Answer
There are many kinds of worms that may be in the pond - earthworms (they drown), blackworms, tubifex worms, horsehair worms, other worms, and then the non-worms that look like worms which are actually insect larvae - caddisflies and midges mostly.  If you could identify the species, that would help.  How big are they?  What color?  Legs or no legs?  My page that has worms on it is at http://www.fishpondinfo.com/micro.htm
The good news is that they are most likely no threat at all to the fish (who should eat them) or other animals including kids.  If the pond doesn't have fish, then adding them will help to reduce the worm's numbers.  There would either have to be a lot of them to eat the plant roots, or they would have to be a plant parasite for that to be the case.  Some insect larvae live on plants.  The best thing to reduce their numbers (aside from fish) is to clean the pond which you said she did.  Anyway, they're probably nothing to worry about.  If you could send me a small, clear jpg photo (my e-mail is on my site), I may be able to tell you more.  I personally have bad luck taking photos of tiny things.  Good luck!

Robyn