Why do you want something to eat sargassum? Why not just prune it? Seems to me I don't have sargassum anymore, apparently I have pruned it out of existence in my tank.
If only I could prune the grape caulerpa out of existence. That stuff is insidious. I don't mind the sargassum actually. It reminds me of the "big sargassum" forests you see out on the west coast and down to California and all that. But the caulerpa .... if I had the space I'd get a foxface because supposedly they'll eat caulerpa indiscrimately. Eating caulerpa seems beneath my tang somehow. He won't touch the stuff. Sigh.