I have a large cleaner shrimp that hunts them in one tank, and they don't come out much during the day. The smaller tank (with no cleaner shrimp) is thick with worms...
Don't think those are a problem... they do serve a purpose, and their populations tend to stabilize - even at what may seem ridiculous levels. If there is a dead or dying snail or small fish, you won't see it and it won't have a chance to foul the tank. They're THAT good.
They clean up the stuff that they would otherwise be competing with another cleaner shrimp for. I prefer watching the shrimp over the worms, but the shrimp is voracious, and goes after pods and pretty much anything else that moves. The worms only clean up (they don't hunt), so they're not competiing for food with your Mandarin or 6-line wrasse, for instance.