yep its not common but tangs or alot of reef fish arent beyond the occasional or rare individual that finds out certain corals are tasty. I think a few strides in available feeding products for goniopora have been made in keeping them more successfully (it doesn't help there are about 20 different species that all have different feeding characteristics) but I agree at this point its still much more likely the flowerpot wont be around next year. the only problem with keeping the tang is I wouldn't want a tang that likes eating ANY corals. who's to say it might not find more corals appetizing. I'd trade the tang for another specimen although I wouldn't expect the goniopora to make it long term either.