How is the pond situated? If it's in the sun the bigger part of the day, it WILL be hard to avoid the algae. But there are a few things you could do x
Buy/build some sort of cover for the pond that would keep it in the shade during the hottest and sunniest hours of the day.x
Get yourself more pond plants! Plants are wonderful because they are consuming nitrates and other nutrition from the water, which will starve the algae
Besides, it looks wonderful with a nicely planted pond
You could borrow some books about ponds and pond-keeping from the library, they should have lots of good info about suitable plants!
For optimum results, do both of these things d: