worm question

I was cleaning out my pondmaster filter and found some tiny red worms in the
coarse pad. They're 1/4 to 1/2 inch long and very thin. What are they? I
don't think they're bad and didn't wash them away. I just changed out the
charcoal pad and rinsed off the coarse pad. I put the filter back together
and returned it to service...worms and all.

The pond seems healthy. I had a fish kill a while back and it was driving
me nuts. But I'm pretty sure it was due to warm water and way too many
fish. Things have leveled off and the remaining fish (9 in 250gal) seem
very content. I have lots of lilies and some other plants I can't pronounce
or spell. The water is very clear too.

Anyway, I'm sure someone can end my curiosity.

--
Pond Diver