Funny you mention that. I added a Yellow Tang (obviously Zebrasoma family like your Sailfin Tang) and it erradicated the bubble algae in about a week. That along with the GHA from the rocks and glass. I had no idea they ate Valonia! said:
Yep. I've talked about it before and recommended people try it for a few years. Even the small ones will help all you need to do is pop the bigger ones for them and they will eat the skins up. As far as other stuff, the cotton candy I'd be willing to say if its edible, it will get eaten. Some algae like bryopsis has anti-predatory stuff in it to discourage animals from eating it but I don't think cotton candy is one of them. I know I have seen them eat the red brillo pad stuff off the rocks and hair algae but they won't go near bryopsis.
I know yellows will do it sometimes but I have had great success with Purple Tangs and Dejardini. Maybe its the Red Sea connection I dunno.
I'll see if I can get a video of these guys in action this weekend its really a sight to see.
As far as the butterflies go. Call Frank and see if has any in... the location of collection helps determine their health and their diet... also get one no bigger than 2" from tip of his nose to the end of his tail. The younger ones seem to be more prone to eat aiptasia.