Hard to tell, looks like a couple different kinds? I think I see GHA or byprosis in there… Do you have phosphates in your water? Are you using clean RODI or tap? How long has the tank been running?
So this is the best picture of the algae I have been trying to name. This algae took over my GSP and is growing on small places in the dT. This picture here is in the sump. It's the spider web thing