Why is there so much algae in my tank????(read details)?

I have a 65 watt light over my 20 gallon tank, use the yeast reaction thingy, have about 15 fish, 3 amano shrimp, two snails(only eat algae according to LFS), and an aquaclear 30/topfin 20. Algae is on then gravel, plants, gl, filters, heaters. There is green kinda hair algae, dark green stuff on plants like hair, Green spots that dont come off. The snails/shrimp really help, but arent solving the problems. I do 10 percent water changes every 4-6 days, added a phosphate/nitrate remover(LFS told me to) and still lots of algae. I am not near a major light source and have cut the lighting to about 9-10 hours.