Is this hair Algae?

[PhishFriends]

Water change and tests yesterday showed nitrates at nearly zero (Salifert) and phosphate at .04ppm (Hanna). I was dosing sodium nitrate and keeping it at around 3 ppm and it had stabilized for over a month. Now it just dropped and this algae started appearing. In my fuge I'm fine with it, just wondering what it is. This is one days growth.
Should dose nitrates to bring them back? Clearly something is newly consuming them. Or just wait?
Year old tank, very little algae to speak of.

 

[Dave1993]

you need to get them nitrates up or your coral gonna go byebye