Most, if not all of us in this hobby have heard of certain fish said to be known to pick on corals & inverts. The largest group we keep that has this reputation would be Pygmy Angels. I have found that this is NOT true IF these fish (& all others) are provided a suitable diet AND are not allowed to go hungry. If a fish is missing something it needs in it's diet they will often start searching & picking at things they wouldn't normally. I've also found that if a fish is hungry they will sometimes display this same behavior.
2 ways to help prevent this unwanted behavior:
1. Feed daily a well rounded diet which will satisfy the needs of all the different fish we keep. It's not hard nor do you have to keep a smorgasbord of foods on hand to accomplish this. I feed only 4 basic foods, but together, provide complete nutrition which meets their needs. See my article "Feeding Reef Fish - What & How Often" for what foods & how I feed with complete success.
2. Feed in the morning. Especially if we have fish that need Nori seaweed. This way they have it to graze on all day & will be less likely to get into trouble looking to fill their empty bellies. Also, if you're using a standard "veggie clip" more than likely alot of the Nori you're feeding is floating around the tank & going to waste. Consider purchasing & using my AquaCorals Nori Feeder which hangs on to the Nori & keeps it available to your fish throughout the day.
I have found this feeding regimen works across the board, including Moorish Idols, Mandarins & every fish you see listed on the AquaCorals.com website.
AquaCorals stocks all the foods needed to have success in not only keeping your beloved fish pets healthy but your corals & inverts safe from unwanted picking behavior.