I currently have two Idols, one for over three years and on for over a year. You have to keep Nori available for them to eat at all times (when the lights are on) and yes they will eat most LPS and constantly pick at new growth on SPS. They like some types better than others.
I have a 375G reef tank so there is a lot of SPS for them to pick at, so it's not a big problem.