What works good in aquariums is hydrogen peroxide. It will not help with the nutrient load but will take out the algae. You can get 35% hydrogen peroxide from a local hot tub supplier.

I would add where you have good water flow a pile of lava rock with your bacteria. This will give you a house for the bacteria to live and stay. Good water flow in that area will keep cleaning the water.

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7/8th of an acre, Perch only pond, Ontario, Canada.