Has anyone ever run into anything like this? My sister and her boyfriend have two baby red ear sliders which went into an old tank of mine about a month ago. Well, my sister decided she wanted to redo their tank, so she got some of my old gravel which I had washed in boiling water and then put out in a bucket in case she wanted it. The gravel was left to sit until today when my sister took it and poured it into the tank. These long stringy white worms swam up from the gravel and when my sister's boyfriend reached in to get the plants out of the water, the worms bit his arm up. I have no idea what they are, all of my searches keep turning up results for planaria. I haven't seen the worms, but from what my sister says, they're at least an inch long each, thin, and apparently vicious. Any ideas?