Yeah, that's valonia. Probably one of the worst infestations of it I've ever seen.
There are a number of emeralds in there but they either don't go after it, or it's growing back faster than it's eaten down.
This tank in particular is just causing me a lot of stress and I think I'm just going to tear it down and convert it into FW. Just too much going wrong in there to try to salvage it at this point.