Install an UVC of correct wattage for your size of pond.

Save money on pond pumps, pond filters, backyard waterfalls, fountains, ponds, water gardening, koi food and how to achieve crystal clear garden pond water too using ultra violet lights and sterilization.

This is a 250 word (approx) summary of a chapter from my book ... The Complete Pond Solver

Like most of us the more food, the more oxygen and the more sunlight the better and bigger the algae grow.

Install an Ultra Violet Clarifier of correct wattage for your size of pond.

Because algae is very small (4 microns) it is almost impossible for a normal filter to remove it.

If water containing algae is passed through an Ultra Violet clarifier the algae are killed and they clump together making it possible for them to be taken out in a good biofilter.

The UV lamp inside the quartz tube has to be replaced after about 8,000 hours use which is every year in practice.