Algae growth is natural and no matter what you do you will have algae when your pond is exposed to any kind of light.
I found that by having my pond heavely planted with lilies, water hyacinth, and water lettuce, the algae growth is minimized. I also have Japanese live bearing trap door snails that seem to do a good job of helping to keep the algae growth in check. The other equasion is not over feeding my 7" to 9" shubunkins. By doing so they graze on the algae on the sides and bottum of the pond more which is required in their diet.
Happy ponding,
Rich