What are the best water testers to use?

a protein skimmer is not goig to fix your algae outbreak. As suggested you need another solution. 3 primary ways to lower phosphates. 1.chemically with some type of media such as GFO perferably in some type of reactor for most efficent removal. 2. Something else that obsorbs phophates such as microalgae. 3. making sure phosphates arent being put into the tank yourself from using tap water or foods that contain phosphates.
Once you have done all these things and your phosphates are still not undetectable than that would be a concern of the phosphates inside the tank from live rock or to much settled debris allowing phosphates to be leached back into the system. you may want to lower your daylight lamp cycle a few hours if you still have algae issue but I would start with the reactor.

 

So I use RO water, so I know its not from my water, I have macroalage so thats outta the question, and So it comes to me having to get a phosphate reactor, but to be honest with everyone, I really dont know what one is, or how to hook one up and use one, or where to even put it?:-X Orrr what kind to buy

 

Well, my dear, why didn't you say so! Here is the one I use; ViaAqua Poly-Reactor (Multi-Media Reactor) It is simple, comes with a pump (most don't) and can be hung on the tank or sump or used as a stand alone. Buy some Pura Phos-Lock or similar granular ferric oxide (GFO) media, follow the directions as to how much to use and your gold.

P.S. shop it around, they used to be $40.00

 

TLF. alos has a popular reactor the Phosban Reactor 150. Installing one is not going to be any harder than a skimmer. You will hook it up to a pump and add whatever media you want (preferably GFO.)

Two Little Fishies Phosban Reactor

Bulk Reef Supply also has GFO Reactors. You could buy the reactor and GFO from them if you prefered to buy them together.

Bulk packaged Granular ferric oxide GFO for aquariums - English

 

I had a algae "outbreak" once. It never got very big. Anyway, it was solved by replacing my bulbs... IME, T5's need replaced after eight (yeah, I said 8 ) months.