Is this cyano?

[Jasongtr]

Noticed over the last few weeks that I'm getting some reddish patches on my rocks, at first I thought it might be coraline algae starting, but I've just noticed some at the base of the rocks on the gravel

Our phosphate did go to zero recently and I've also just added some corals so dropped the flow so as not to blow them into the atmosphere...

 

[Jasongtr]

Just went to see if it would blow off the surfaces and it's gone away easily, still would like some insight on what it could be though

I've turned up one of the gyres too as I understand cyano to thrive in low flow areas which would explain where I found it