Looks like staghorn. Manually remove as much as possible. As you probably dread hearing, CO2 is probably your issue. If situation is really bad, do a blackout to really blow the algae back and then add fast growing plants and a lot of them. Make sure you have good flow around the tank. Also reduce lighting.
it looks more like hair algae than staghorn, sounds like you are on the right track though
I agree it does look more like hair algae. With the changes I made it seems to be held at bay and my shrimp seem to be cleaning what is left over. It looks like it is turning white instead of green which I think is a good sign.