Hi guys! I seem to have a problem. I have a koi pond, and at the waterfall base, there are little green worms that are attached to the slate/rocks. I saw this and i decided to scrape them off with a small rock. Well, they sort of curled up into a little U shape. When i DO scrape them off, they can swim! They have a green line down the middle. I highly doubt they are black fly larvae because they arent black and they're really thin. Any ideas on what this is?
