I think most people have bubble algae, in some cases conditions may not be right for it so its in a hibernation state until conditions change and become more favorable. I just rip it out like any herbivore might do. I find that it spreads regardless of how its removed, but at the same time its being controlled. Emerald crabs may help, and there are several herbivorous fish which have been demonstrated to eat it, but if this in the 35g most fish will be too large to put in. Try scrubbing it outside the tank and give it a good rinse. Either that or dont add the rock if you're concerned about it.