snrub, I think general consensus is that they don't really harm the healthy fish in your pond, but may go to town on sick or dying fish.
They can be a nuisance eating feed, or when fishing or swimming, but I just leave 'em all in there.
Excerpt from Robert Crais' "The Monkey's Raincoat:" "She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."
