Biomatic pond filter: The pond filter experiment

Just a short note here. The “pond filter” mentioned on the slow sand filter site slowsandfilter.org has been working for 15 weeks. The thing is put together without the elaborate “baffle” pipe assembly and using .35 mm effective size sand. It has just a flat piece of slate rock sitting on top of the sand that the input water splashes on instead of using the baffle pipes to keep the water from disturbing the sand surface. The filter’s top sand surface remains undisturbed. The water is clear and the birds love it. A coliform test will go in shortly. Since the water is always splashing and completely recirculated from the bottom up every 24 hours, there are no bad insects like mosquitoes breeding in the water. The whole thing, including the small fountain pump cost under 100 dollars. The main purpose here is to determine if this design is effective in removing coliform bacteria.