Kill it, Kill it, Kill it! Drop something really heavy on it (after you remove it from sump/tank) or make spaghetti tonight and play bristle worm roulette............with your friends............but don't tell them.
On second thoughts can I buy that bristle worm off you, I'm making myself think there may be some fun and frolics to be had.
Huge? No...those are but little babies! If you want huge, put one in a bowl, feed it every day, and you'll have a foot-long, finger-thick one in no time.