I just wanted to share my cousin's filtration setup for his koi pond. Didn't cost him much since his family run's a water purification business. Funny thing though, even with all this filtration, he still has problems with parasites because of all the frogs in their garden.
At least his pond is algae-free even in direct sunlight.
The white container to the right is his DIY canister filter with lots of filter wool and ceramic rings.
These things, whatever they are, filter out crud measuring microns. Talk about being obsessive.
I wish I could afford something similar.