Here is the response I got from Dr. Ron Shimek:
Well, I really can't help you. Identification of small foliose algae from images is damm near impossible. One really needs to look at the microscopic structure of the stuff. There are simply a lot of diffierent varieties that have similar growth forms found in various seas, and a lot of these can find their way into our tanks and grow there. Such algae are common in the real world, but they haven't been ecologically investigated very much.
Personally, if I were you I would worry not at all about what exactly the stuff is. In most cases, snails don't eat this kind of alga. In fact, very few animals of any type do; red algae often have chemicals in them that deter predation. The natural predators are likely herbivorous fishes, but I really don't know of any animals that eat these algae reliably. If it bothers you, I suggest you scrape and siphon it off the rocks.
Not great news unfortunately. I have been doing some research and it seems that the red stuff may be Asparagopsis taxiformis
and that Mexican Turbos (Turbo fluctuosus
) seem to eat this stuff. At any rate, even if they don't eat it, it won't hurt to throw some in as I don't currently have any in the tank now.
Hmm... Man I really hate to try and remove the rocks and scrape this stuff off. Moving rock work around the inside an acrylic tank can be troublesome. I might as well start putting matching scratches on the outside.