Can anyone help with algae in my Reef Tank?

[haze]

So I have a 75 gallon reef tank. It has live rock, corals and fish. It has been up and running for over a year. Every few months I will get algae that grows like a mat over my sand (dark brown to red). I have a sand sifting starfish and pink spotted watchman goby that keep half of the sand free of the "mat". Is there anything that I can do to keep this from happening? It doesn't bother anything it is just an eyesore. Like any other reef tank I keep my nitrate levels as low as possible. The highest they ever get is 10 and whenever they get this high I do a water change to lower them. Anywhere between 10 and 25%. I add calcium and strontium for my corals I have a Rena XP4 and T5 lights. Any suggestions would be greatly appreciated.