I'm no expert but I have done a lot of research. I would test you nitrite, nitrate and ammonia level. High levels of nitrate will cause your algae to flurish. Try cut back on the amount of light. If you have the sun shrinning on the tank, block it. If you have corals or anything that require a lot of light, do not cut the light, except the sun light, it will kill your "light lovers". Try and invest in some "cleaner animals" like a cleaner shrimp or snail. Make sure the new animal is compatible with anything in the tank. If you have brown algae keep you phosphates below .1 (.03ppm) or use astrea snails: 2-3/gallon. A tang or surgeon species of fish will feed on the green algae.
Good luck!
Chad