Steve, This looks like cyano to me, I'm sure others will chime in. I'm not sure how big the tank is, but 10 gl a couple of months ago probably isn't enough on the water changes. Most people here do 20% or more around every 2 weeks. What type of skimmer do you have? What is your bioload? It looks like you could scrape some of this stuff off and vacuum it out with a water change. You probably need to do 20 - 25% water changes for at least 2 or 3 weeks and scrape the algae off prior to the changes. Also, what is your substrate? If you have sand or
crushed coral you need to vacuum it out when you do the water changes.