So, last night after dark I got my headlamp out and started some snail maintenance (removing the unwanted ones). I peeked under a Lilly pad and was surprised to see a 4-5 inch, thin, worm kinda thing. I kept watching and pretty soon I notice its kinda flat on the top side and it starts swimming away! It was moving and now looking like a small eel! If an eel, I have no idea how it got into my pond - but I suspect that eggs may have been carried in on bird or purchased plant. Anyone have experience with this? I'll try again tonight to get a picture. It seems very elusive, though. I've read that eels will eat your fish when big enough and can take over the pond. Yikes!