Actually I have a 4" adult in my tank. I also know someone else who has had one in their tank for a while. I had read that they can be picky eaters, but I have never had a problem getting mine to eat. He will even eat frozen food directly from my hand. When I first got mine in January, he was eating spirulina enriched brine shrimp, PE mysis, and Rod's food herbivore formula. He now will also eat Spectrum pellets, Ocean Nutrition Angel formula, and anything else I put in my hand. The only thing that mine will not eat is Nori.
I have a 180g tank and he was my first addition, but has thrived there. I can only tell you from my experience, but I have had success so far with mine.