2 stage sand filter done, got room for a 3rd, and figure that should go for charcoal. For now it's collecting, or will be once it saturates, the clean water. I've got that branch that fell on my DSL line last week, not sure what the city will say but may have to chop it up and make my own charcoal to further the "test" as i doubt there would be much chance to buy it in the store - course without a beach I don't know where you'd get the sand at in the first place.