If I may add, my Yellow Tang changes color sometimes, too. He sometimes goes a pale-creamish color. In the morning, he has a little cream-colored line running horizontally over his body. I think this is normal. Sometimes, he will show signs of fading in color around the nose area, but this will soon go away. I feed him a little flake food in the morning and a dose of frozen brine shrimp in the evening. He's doing very well!