So I've had various tangs in the past. They would instantly devour anything plant-based I would put in the tank. But in my newest tank I have a Scopas and a Tomini that are "different". They won't touch nori. So a week ago I tried to attach a bunch of Red Gracilaria to a rock, and they won't touch that either! They will literally pick algae off the same rock, but they will not take a bite off the Gracilaria. Anyway, I do feed them pellet and frozen food so it's not like they are starving but I'm just baffled by their aversion to what would be their natural food in the wild. What gives?