Bev,
If I lived in Edmonton, I'd volunteer to watch your tank for you since I'm usually up till past 2am working on the computer anyways. Good luck. Remember, no mercy. Kill the b@st@rd worm.
Maybe even try baiting a stocking/netting trap with a couple of snails. Remove all the remaining snails from the tank & after a couple of days of hunger, place one or two inside a ball of stocking/netting & see if the worm entangles itself in it.
Good luck & happy hunting.
Anthony