While kalking some aptasia, I decided to try it on some of that pesty calurpa that keeps growing & choking everything. It worked! Totally dissolved & is gone now.
This is the stuff with the tiny flat leaves, not the grape but I think it should work on any of them. I'd pull out as much as you can by hand 1st. This small stuff is really hard to get off the rocks though. I think the grape is much easier.