Algae is going to be a fact of life if you're growing live plants. But you can cut it down and keep it under control by finding the right balance for your little ecosystem. A big algae problem is usually a factor of too much light (running the lights for too many hours per day) or having too many nutrients in the system for the amount of plants feeding from it. You may need to cut back on your lighting, inject CO2 to stimulate vigorous growth (if you have high lighting), cut back on dosing your ferts, clean out accumulated waste, or add more plants than what you have already.
For us to help you figure out the best solution, please post details about the lighting you have, you tank size, how long the lights are on, what amount of natural sunlight is reaching the tank, what ferts you are using (if any), the dosing schedule you follow, what kind of plants you have in there, and how many of them do you have. If you could also show us a photo of your tank, that will help us get a better idea of this as well.
