and found that there are at least a zillion
of these...They are about half an inch long and very white looking... What do
I do now?Will the Koi and goldfish eat them?

Only if you are very very lucky,,,I had some minnow come into my ponds on
plants, and they have been a headache for many years....I catch them in a
butterfly net and throw them by the hundreds onto the lawn for fertilizer, and
bird food......there must be thousands of them in all the ponds now I have even
drained the ponds, but some manage to survive and all it takes is a few to
start the whole process over again. Jerri

http://www.fringeweb.com/Ponds/JerrisPond