Yes, this helps a lot and definitely worth a try.
How old is the tank-
My tank is 4 months old however, some of my fish are over a year old. I had a 45gal tank before this one. Everything got transfer over to the current one 91gal. So to answer your question, My new tank is 4 months old with livestock and rock that came from a 1 year old tank. Hope that make sense.
what is your feeding schedule
I feed one cube of mysis shrimp with one sheet of Nor. I also had a automatic feeder however, is now been removed.
what kind of live stock do you have?
Small Yellow Tang
Small Blue Tang
Small Yellow eye Tang
2x Clown fish
Diamond Goby
One Spot Foxface
Side Note: I was running GFO after I tested zero Phosphate, I stop running GFO.
At just at a years time I suspect the rock may still be leeching a tad depending on how high the po4 levels were in the water column in the old tank and for how long. In order to successfully take the organics out of the Rock, the amount in the water around it must be lower than the reserve in the rock. Remember as I said osmosis moves from areas of high concentration to low concentration. So if the levels were higher in the water than then rock, the rock will actually absorb it. It may not be that severe though, so for our purposes let’s just rule that out as a source, but it’s very possible it still is. It won’t change our plan though.
Those fish that you have are also a problem. While a single yellow tang would probably be ok, combining it with a blue, a kole and a foxface is a problem. They may look small but given the amount of energy all 4 of those fish need in order to grow, they eat a LOT and extrete a LOT. So bioload is the first thing I would list as a problem. You need to take some of those out. Especially the blue. The yellow or the kole would work but not Both. I would also re-home the foxface. So, loose the blue tank, and out of the kole, the yellow and the foxface pick one.
Feeding wise, is that one cube and one sheet of nori a day? I would cut that back. Feed a cube every couple of days and move the nori to twice a week. If you drop the fish load as outlined above this can be done easily.
So that’s how you fix your nutrient intake. After this has been addressed, douse the lights in the display and move to taking care of your export as outlined below.
Now let’s go over output/export.
The hair algae is taking the lions share, but it’s ugly I know. So we have to somehow move that to something we can control.
What kind of skimmer do you have? I would do some research on whatever you are using and make sure that your skimmer is a quality unit and is appropriately sized. Adjust it a little if it is a good skimmer and start skimming very wet for the time being. If it’s undersized and a known poor performing unit, invest in a new one. CLEAN this sucker every single day or every couple of days for the time being as well to maximize efficiency.
Bring your GFO back online. As I said you are reading zero is just because the hair algae is taking the majority out of the water column. Once the algae starts to die back, and phosphates start roaming free, the GFO will pull it out. Also, it can be helpful to run two po4 tests while your going through this. One on the sump itself and one on the direct output of the GFO. Once the GFO output starts climbing, it is exhausted and it’s time to change it. Depending on how much po4 will start flowing around the water column as the hair algae dies the GFO can exhaust in as little as 24 hours, so make sure you keep an eye on it and change it as soon as the output reads anything except a goose egg.
Water changes should be done frequently. Even daily. Large enough to start diluting things. While you are changing the water, suck up everything you can with a gravel vac, blow off the rocks with a turkey blaster before you start and crank those powerheads. Get all that crud up in the water and suspended so you can suck it out too.
Running some filter socks is not a bad thing either as long as you change them daily or every other day. This can help catch that nasty stuff and you can export it easily between water changes.
As you start seeing your hair algae recede bring your chaet reactor back online. I would slowly ramp the lights up in the reactor over the course of a week or two rather than just blasting it. Macro algae is a lot like potted plants. Photosynthesis is not a passive process. It requires energy to do, much like the Krebs cycle in human beings. If the plant is not getting enough energy in the form of dissolved organics, blasting it with a crap ton of light will kill it. The photosynthesis of the plant will kick into overtime to try to convert all that light, then it will end up in a negative energy balance and waste away. Ramping up the light will let you find the balance of how much photosynthesis the plant will be able to do with the available nutrients. If you start seeing the plant recede on the lowest settings, turn the light up until it starts to grow. After you see the plant start to wither, turn the light back down and keep it there.
Basically, by doing all this you are trying to transfer the nutrient uptake from the hair algae, to artificial things that you can control like the GFO and the Macro algae. After the algae is gone, and the po4 is being exported by your GFO, Skimmer, water changes and Macro algae, you can start worrying about the no3 level. Tackle one thing at a time, trying to address everything at once is going to just be a massive failure and lead to frustration.
It could be the light strip was not strong enough or the flow. To eliminate those possibility. I bought a new Skimz algae reactor just in case light was an issue or the flow. Is a week old and I have not looked to see if Chaeto is growing. 
