I have a 125, and keep 4 tangs. 3 yellows, and 1 palani, I have no problems with aggression. On another forum everyone said I would end up with one. That was almost 6 months ago, and there still going strong. As far as that PH
it kind of seems strange. Not saying it couldn't happen, but maybe it died and then was sucked onto it. Also if this one doesn't make it, I would have to suggest you getting a medium regal. There hardiness, and tank suitability increases with their size, and the small ones generally eat off the rocks on alage. If it still wont eat algae sheets off a ruberbanded rock, I would soak some in garlic. It may entice its appetite, and get the little guy eating. I hope he makes it.