Is my Kole Tang Eating?????? HELP!?

I have a 125 gallon aquarium with 55 pounds of live rock. I recently got a 4 inch kole tang and he was getting picked on by my yellow tang so i returned my yellow tang just for him. I realize he grazes on live rock but i dont think i have enough so ive benn putting 2 different types of seaweed on a clip. I cant tell if he or the other fish are eating it. I have never actually seen him eat it. Every now and then he eats a little brine shrimp. What should i do and is there any other foods to feed him?????