Beth,
Not that this is what you're looking for, but I thought I'd mention. I used to feed my seahare those little algae wafers. I forget what kind of algae they are made of but they're just called "algae wafers" (they're for herbivores and they're about 1/2" in diameter.) I would crush them up into smallish crumbs, then I'd have to hold them in front of him. It would have to be right in front of him for him to notice it though. I'd feed him at least a wafer or two every day or two.
I've since stopped feeding him directly because he has discovered the nori stick and will eat off that now. So if you can't find any hair algae, give this a shot. It took a while before he ever ate nori, but the algae wafers he took to, right away.
HTH and good luck.
