Yes, it is definitely Valonia. Manual removal is probably your best bet as I've had emerald crabs ignore the algae and head for other, tastier items in my tank
If I was to add a emerald crab would it try to kill my fire shrimp? or my pistol shrimp..? Unfortunately must've been on a frag plug and I could pull some of them out but they would only grow back and some are so small to grab I think the crab could only grab it..