Saltyfins, I am going to give you my opinion but you are not going to like it and neither is anyone else. All of these things we experience in this hobby, especially a new tank like yours is natural, normal and expected and they come and go in cycles. Some cycles last a few weeks and some a year or more but they all go away.
The stuff you have growing, whatever it is, is not going to effect the health of anything except yourself. That is unless you start to add chemicals that are not natural and everything man made that comes in a container is not natural.
I have spent almost 400 hours under water and have seen everything growing in the sea that we see in our tanks. My tank is 55 years old and I have way more algae and cyano than you do. Do you know what I do? Maybe have a glass of Pino Noir and go out to dinner.
I also never test because then I would tweek and the tanks with the most tweeking have the most problems and tank crashes.
So my advice is to do nothing. You can suck out whatever comes out easily if you like but I would not add any chemicals. It will straighten out. All you need in there is seawater. Give it a chance to straighten out by itself, maybe limit feeding and be sure to rinse the food which I hope is frozen food and not dry foods.
Here are some shots in my tank, notice the algae? Everything is healthy, nothing has ever died from a communicable disease in 45 years, most fish are spawning even the 35 year olds and I have had so much algae that I could open a produce stand.
I took this on one of the outer islands in Hawaii.
This is behind my house, every rock has 3" of algae on it.
