New light would likely make it worse. Just sayin' from recent experience. I got a piece with cyano on it early this year and learned that chemiclean did a good job. It also affected the hair algae. I'm also in the later stages of a Kent Tech M treatment currently which, although slow, is showing good signs of cleaning the whole tank. I'll be doing another chemiclean treatment later today.
As a gardener, know your enemy:
http://www.reefcleaners.org/nuisance-algae-id-guide has been helpful in figuring out which ones I have and how to deal with them. In retrospect, I should have been more aggressive early-on with the toothbrush. A cheapo submersible battery toothbrush would have been perfect, if there is such a thing. I had the misfortune of being poisoned by a neighbour with an organophosphate and ended up in VGH almost dead. While I was there, my mother decided she was going to feed the seahorses. With her hand tremors and turkey baster overfeeding combined with the death of a softball sized Sea Hare led to a massive hair algae outbreak. Even though I was sent home unable to walk, I immediately did a 50% WC followed by 25% later in the day and another 50% the next day. The deep sand bed held quite a bit of crud. A few months later, the tank is virtually algae free and the macros are doing a good job of stealing what's left of nutrients from the hair. When I installed my new LED, I turned it too high and lost a Monti. The hair algae has also been quite robust. I've been regularly doing the toothbrush scrub and mag-float scrape with great filtration from a canister with UV.
I hope you do get a handle on it. It took me some time but I have won the battle.