Mine lives almost entirely on NLS pellets. I also mix in some Formula 2 pellets also, but my angels eat most of them. Sometimes I will give Nori, which I have found helps with pennant growth.
When mine was younger, it needed a lot of feedings. Now that it is older, it gets by on 2 feedings per day, but i overfeed so that there are a lot of pellets on the bottom and it can pick on them throughout the day. I agree feeding often is key. Also, don't let other fish out compete the Idol for food. I have removed fish that ate so much there was nothing left for the Idol.