just imagine planaria but a much deeper red and about 5 times larger. very scary LOLCan I see the picture of this kind of worm? Havent see it before.
I found two in my tank years ago, removed them, never saw them again. I recommend you make a trap first before you nuke the tank... either use a glass catch pen or make your own trap. google around planaria or leech trap and you'll find plenty of diy tutorials.