Depending on what you might mean by cleaning the filter, you may need to stop doing that. The only thing you should do is lightly squeeze out the pads in some pond water in a bucket. You should not be rinsing or cleaning the bio balls as the sludge that builds up in that area filters the water for you. Instead, try changing 25% of the water every other week, to help reduce the amount of nutrients in the water, and clear up the algae.
Algae is caused by excess nutrients, so you may be over feeding and need to cut that back. That being said, full sun will definitely cause a lot of algae in a pond. You did not mention what type of algae you are having a problem with, and that can be important information as there are different ways of tackling different types of algae. If it is green water, you could try Tetra Pond Water Clarifier or Tetra Algae Control. If it is string algae, I would recommend removal by hand along with Algae Control.
Increasing water flow can definitely help, so an addition of a fountain or a second pump simply circulating water may help as well.
Date published: 2016-08-22