YES!!! Very important point. UV clarifiers are NOT filters. If anything they
just contribute to the bioload of the pond.

Hows that. I can think of few things that deposit more bio-load than a
pond full of suspended algae. When it is finally starved of a food
source and dies away, it settles to the bottom of your pond

Why do you think that? I think it just rots away. What do you have, redwood
or cedar decay-resistant algae? :-)