If its not slimy it is probably just diatoms. Pretty common in a new aquarium. I had the same problem when I first started mine, after getting adequate flow in the tank it disappeared for me.
Random Algae Tips:
1.) Check your parameters and make sure they are inline with what they should be. High phosphate and nitrates will cause algae booms. Act accordingly.
2.) Decrease your lighting schedule or complete turn off the lights for a few days. Note: This is easy if you only have fish in your aquarium, but for a limited time wont effect corals as it is not sunny everyday on the reef.
3.) Feed sparingly for a week or 2. If your using frozen food, make sure you can straining it as the liquid in frozen foods tends to be high in nitrates.
4.) Water changes, this helps remove the nutrients the algae is using as food. Once the food source is gone, so will the algae. Also, make sure you are using RO water and not tap water. Some tap water has nitrates and other impurities that can cause algae to grow.
