The hydroton keeps the bacteria and such going, which is great. But sucks for water clarity as it always seem to have dust particles and such coming off. To fix this...and I am super cheap, some call it ghetto...but anyway. I went to walmart and bought the NON biodegradable quilt batting. Like a $1.50 yard. Before returning to the pond, the water is pumped over the batting and it picks out the larger particles. When it stops working, rinse it out. Can reuse it several times before having to replace it. Cheap/easy and it works. How often you change it depends on how nasty your water is.