I would almost call them bull it proof. Many years ago, I had a small one that was about 1' long and about as small around as my little finger. It used to always wind up in my HOB overflow or down in the sump until 1 day it was nowhere to be found. I followed its slimey trail on the carpet about 60' around the perimeter of the room and to behind a bookshelf in another room. It was eel jerkey when I peeled it off the carpet and threw it away. The next day the guy at pet store told me if it was still sticky I should have put it back in the water so when I went home I retrieved it from the trash and put it in a bowl with tank water. He was back to swimming around in less than an hour and lived for several years after until I sold all my livestock and tore down the tank.