ten years of online algae battling threads fw and marine summed up:
algae growth is nearly always viewed as a negative inference about some aspect of nutrients or tank params when thats the rarest case. algae exploit, so they are constants.
importation ranges and is varied, so one tank gets spiros and another gets bba on and on. the lucky seem to inherit nothing but pure greatness and dont have algae problems, they are in the mix too.
of course nutrients and limiting factors can be used to boost or lessen undesirable algae growth. for marine the current big deal is limiting phosphate. in the 2000's it was limiting nitrate. fw views tend to ascribe algae issues to *lack of certain nutrients in their quest for indirect control, and prevention of algae.
some facts remain about algae control through the years
you have the power to hand remove always, and in fact thats the only thing guaranteed to work. Throngs of threads w always exist on how to prevent, find causes, identifications of algae, and thats fun to keep watching evolve. but the answer to your direct question is the cause of your unidentified strand algae is importation unknown at the time and nothing wrong with your tank. making the countless counter adjustments to battle it is common, but is an indirect method, so its so so.
but this one tank keeper who hand removes, or chemically burns, or ensures the tank simply has no algae- has no algae to speak of, just a pristinely clean reef and planted tank. he or she may or may not spend a lot of time doing removal work, depending on their luck and planning. so the answer is you should just remove it all if you want it fixed. id peroxide burn it but thats just me and Im biased.
learn to see algae battles in two modes: that which prevents, and that which removes. dont confuse the two, most do. whether the tank is 1 week or, or 800 weeks old algae battles come down to the same distilled events> either choosing or not choosing to instantly remove any algae that can become a problem. prevention of algae is where you get ten thousand opinions.