Tangs do nothing but eat, poop, swim, and...Grow. I have two sheets of sea weed (green, red, or purple) either warped around rocks or hanging from a clip, at all the time for my tangs to graze on. In addition, I feed them at least twice a day varied diet (pellets, flacks, and frozen food). I am sorry my friend, but I must agree with all the comments here, Your tangs are starving. The good news is that they are fast healing, and as soon as you start feeding them, they will come back fat and happy. Best of luck!