To control the algae, you need to eliminate its food source. Those would be the nitrates and phosphates. You should be very sensitive to even small concentrations of these compounds in the water because most of them are being consumed by the algae. Any remaining nutrients indicate that the algae cannot keep up with the nutrient production, and cause more algae to grow.
You can add animals, such as lawnmower blennies, to eat the algae, but this does not address the root cause of the problem. The animal will eventually excrete the nutrients back into the water and feed future algae blooms.
There are several methods to reduce the source of nutrients in your system. Here are a few:
1) Increase your protein skimming or add ozone to your skimming. Be sure to thoroughly research ozone use before trying it. It will increase the extraction of organic compounds in the water column, but it may go too far. Protein skimming alone removes organic compounds which can feed algae.
2) Add macroalgae to the system. The idea here is to add algae that will consume the nutrients without being unsightly. There are several algae available for this purpose. Be sure to choose one that does not cause blooms of its own. Choose something that is fast growing, but will not take over the tank.
3) Chemical absorbers can be used to extract nitrates or phosphates. For phosphates the iron based products are more effective than aluminum based products (See this article:
http://www.reefkeeping.com/issues/2004-11/rhf/index.php ).
4) Increase water changes. Simply replace the older water with new, nutrient free water.
This is not intended to be a complete list, but should get you think in the right direction. One other important thing to note is that the nutrients can be building up on your rock. High, chaotic water flow can help keep the nutrients in the water column where the skimmer, macroalgae, or absorbers can do their job.