Algae Problems. I need HELP!

[Hanzein]

I need some help regarding my tank. About 3 weeks ago or so, my tank really did well and I saw some great growing results from my coral and anemone. I don't know what went wrong, I started seeing growth on my sand bed, almost looks like a red Cyano, this is what I think it is, but I dont know. I have posted some photos for reference, they are not the greatest but i am hoping you can help me point out what I am dealing with here. A friend of mine thinks its Cyano Algea. I do weekly water changes about 20l. Ill syphon the sand bed and clean the windows, within the next day or so my sand bed looks like it hasnt been vacuumed for weeks on end.

He suggested that I should do a total blackout for a few days, so I did that for 2 days and when I opened up my tank, almost everything was gone. It really looked great. I started my light cycle for only a couple hours and keeping it on longer day by day.

I have read up on Dinos and I dont think its Dinos as the algae dont go away when the light is off, the same amount in on the rocks and sandbed, regardless if the light is on or off. My coral isnt happy either and they are barely opening up.

I need some help.

Tank Red Sea Max 250
Coral: GSP, Pin Cushion Mushroom
Malificent Anemone.
2x Clownfish
1x Bicolor Blenny
bunch of hermit Crabs
Snails, mostly turbos
Coral Bandit Shrimp.
I have a small in tank refugium that is full of Cuelerpa

PS I did a water test about a week ago, Phosphates were a bit high, Nitrite and Nitrate was fine and my Alkalinty was super low, I started dosing Alkalinity.

 

[Mr. Mojo Rising]

What do you have for flow in the tank? Cyano loves low flow, would suggest to turn up the flow. Chemiclean gets rid of cyano, but you have to solve the underlying issue's first or it will just come back.