I consider Bristleworms an essential component of my clean up crew. They quickly consume dead, dying, decaying organic matter. Years ago, I used to actually buy them... until I figured out that they're virtually impossible to avoid. Let 'em be.
Oh, and leaving your velcro type cleaning magnets in the water can be a bad idea. Eventually, you'll get small tube worms or something else hard growing on it, and scratch the heck out of your tank. Been there, done that. I use Tunze magnets these days, and I try not to leave them in the water.