Rule of thumb is to size a filter and pump and UV lamp to pass the volume of water in a pond every 2-3 hours, but have always had "green water". Just finished pond in our new house and because we now have a waterfall, have a 4000 l/itre / hour, 4500 litre /hour filter and 4500 litre/hour UV lamp for a 750 litre pond, so plenty of flow and UV action -- no problem. Wrong !!. After a week, water is green already and algae sticking to the sides.. Any help or tricks anyone. (yes UV lamp is new and working). Any water creatures that eat algae??
I believe one way of keeping it clean is some barley straw which you often see in small bags in garden centres.
Often seen bales of it used in larger bodies of water.