Best method is to mechanically remove the algae by scrapping. Do not use chemicals or products that will harmm your water quality. You can also avoid using the light too much.
To start to controll algae you need to make sure you are taking all the steps to having a clean tank. This means having a protein skimmer, and some sort of live sand to help with the process. The addition of a few herbivores like hermit crabs or snails would also be beneficial.
Keeping algae from a tank can often times be very frusterating. Mature tanks that are exposed to light build up algae quickly. Having certain fish, such as plecostomus, can actually help because these fish may feed on algae in the tank. Beware though that they will increase ammonia levels.
Make sure there isn't direct sunlight going into your tank, that is very bad for it, also decrease your light, run it for like six hours max a day, also try turning it off for a few days.
The first thing to watch for is light, espicially sunlight, that is very bad. Also watch for how long your light is on, normally I set mine for 6 hours a day to prevent algea buildup, also only use R.O. water.
