That looks just like my tank a few weeks ago. Ironically, it's the same age as yours.
I tried lights out, increase W/C frequency, take out the sand, limited feeding, and scrubbing all the rocks. I repeated these methods for a couple of times. It only helped for a few days, and the algae came back even more stronger.
I followed Sk8r's thread about using NoPox and started dosing that also. While dosing I also turned the lights off for one week. I'm only 2.5 weeks in the process, but I can see that all of the algae died very quickly. I started with 5ml/day and have cut back to 2ml/day. I plan to monitor the algae growth and decrease the dosage slowly over the next few months.