cant stop cyano so i want to try reactor now

I had this same problem when setting up my tank my friend, my tank is now 6 months old.

The problem comes from if you made your salt water using tap water. The solution.

Leave it! once all the nutrients are consumed the algae will die off. dont try suppliments they wont work. if there are those nutrients in the water it doesnt matter what you do, it will come back! (unless of course you some how get rid of all the nutrients)

normal lighting on always and try vaccuming it up and cleaning it off the rocks (toothbrush works best) for the time being if you're really concerned about looks.

water changes using de-ionised/distilled water only or if you live close to the ocean like i do... sea water!

it will get to the point where your tank looks terrible and covered in a thick brown sludge. keep the filter going and the protein skimmer on. at this stage it will peak, using up all the nutrients in the water and than start to quickly die off as it starves.

at this stage it must be removed, clean it off with a tooth brush and siphon it out of the tank. a little more may grow but it'll be much more controlled and no where near as fast.

now for the clean up crew. as i said i live close to the ocean where we have rock pools that house thousands of astrea snails (or similar looking). so i went and took around 10 snails. over the next few weeks they cleaned up all the rocks nicely and i have never had a problem since. my tank is a 3 x 2 x 2

hope this helps