What is this white stringy goop?

[sapphireminer]

For the past 2 weeks, this white stringy stuff has been growing all over my rocks and getting longer. All inhabitants seem to be doing okay, but it doesn't look great at all. Had two bouts of cyano and treated with Chemi-Clean successfully before this...so definitely helped to foster some sort of imbalance. Thoughts?

Here are some stats to help with a diagnosis and course of action:

• Tank is about 7 months old
• Dosed Chemi-Clean twice 1 month apart to treat cyano
• Most recent stats: kH 9.2, Ca 459, Mg 1545, NO3 0.41, PO4 0.03
• Feed a pinch of flakes every other day for the 2 clowns
• Use PhosGuard and Purigen, replace monthly and ROX every 2 weeks
• Dose 0.5mL NO3O4X every 2 days (I should probably stop dosing this given Purigen and PhosGuard...probably making this issue worse, right?), 1mL AB+ daily (coral colors are nice), All for Reef 2.5mL daily

 

[Absolutely Fish]

Looks like dying hair algae.