Green clumps of (hair?) Algae

[MitchM]

I wonder if it is hair algae, then.
Any chance it could be a beneficial macro algae? Can you describe it, or post a pic?

I'm not an R/O expert, but I wonder if ammonia added to the water system could cause a carbon block in a filter to leach PO4... (stab in the dark..lol..)
Post your water tests when you get them, too. (both tank water and source water)

Mitch