Honey,

I don't know about ponds, but you may post the same question in "Ponds and Garden" rather than in "Aquarium".
More chance there to get more help.
Sure you will find some replies here too, later on from people who do have ponds AND aquariums.

So sorry I cannot help you with this.

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:

There is a liquid shade for ponds.  It helps keep algae down and also if your pond is in alot of sun it acts as a sun reflective as it turns the water a blue color.  You can also buy algae treatments for ponds.  API makes a great product to reduce algae.