Planted Tank Guru
Join Date: Jun 2012
Location: Gainesville, FL
It's hard to tell from the images but most likely a hair algae, Rhizoclonium or even diatoms. The lighting seems pretty high for it to be diatoms but not impossible. How long has it been setup? New tanks generally have problems with this at first then disappears after 2 months or so.
Generally you need to dose more nutrients. NO3 of 0 is not a good thing in a planted tank. Low nutrients, high light and DIY CO2 is "the perfect storm" for algae problems.