Yeah, I think I got lucky with mine. He only seems to eat formula 2 flake food and nori... not that i'm complaining, but he's started to ignore everything else.
Be careful with cowfish, they can release toxins when stressed or when they die. Some are more toxic than others and their size matters in relation to the volume of water, but they all release toxins. Cool fish though, the southern australian boxes are by far the coolest I have ever seen and super rare. They require pretty cold water too.