First I would refer you to the helpful articles. there is specific information there to explain the science/chemistry/ cycle/process of it all. once you understand what causes the problem you are having then you will be able to grasp the fix. do read the articles marked for beginner systems etc and specifically the articles on algae, there are several. check you water parameters. if you have nitrates, phosphates, or silicates, you need to address thoes issues 1st, otherwise the algae will dissapear when the food source is removed. for now work with your water quality to correct the problem. hope this helps. if after reading the helpful articles you still are not clear. post back here with specific information and we will try to help you. at this point and with the information given the problem could be neutrients, cycling processes, amonia is also a food of sorts. keep us posted. pics would help.