Hair algae, and how to remove it is a long story. First, don't use tap water, don't overfeed, as close to weekly water changes as you can do, manually remove it by scrubbing with a toothbrush and sucking it out during water changes. Turbo snails have been known to eat it. It is caused by phosphates (which come from fish waste, fish food, and I have heard soap on your hands) and nitrates. Neither of which will probably be present in your system because the hair algae is consuming it as rapidly as it is made.