Absolutely gorgeous Dario !
If your not already (and you may be...) keep a sheet of Nori hung daily or every other day a least... with a few drops of Vita-Chem on it for the Herbivores
here Lee's tips for the tangs too
feedings of gut loaded brine shrimp, mysid shrimp, Cyclopeze, pods, plankton;
feedings of vegetable products (Formula 2, broccoli flowers, Herbivore foods high in vegetable matter);
feedings of seaweeds/algae (vary the colors: red, green, purple, brown, etc.) on the clip, attached with a rubberband to a rock, etc.