We have had our pond for quite a few years and have had problems with keeping the water clear so finally bought a filter with a uv light. Of course the UV light doesn't last that long maybe a year or so.
We bought a new UV light last spring and realized we needed to replace it again this summer in July. I told dh that maybe we should get rid of the pond because I was tired of the upkeep on it. Anyway we noticed that a lot of the green algae on the liner was disappearing. I thought it was rather unusual since there has always been a lot of algae there. Lo and behold we noticed that the water was getting clearer and we can now see the bottom and the fish swimming around.
So i'm assuming everything just balanced out.