DIY 5 gallon slow sand filter update

Back in September of last year, we started 3 small 5 gallon slow sand filters. They are still running, and marginally cleaning the water that runs through them. So far, the best water quality is from filter 10b, followed by 10a, and then 10c. They do work, but only just barely. If this were all you had to clean the water you use, they would absolutely be better than nothing, however they are very sensitive to any physical movement, and the flow rate must be extremely slow for these small filters to do any good. If the input water is turbid, they will plug up quickly, as it is necessary to use very fine sand in these small filters. Perhaps a good way to run them is to use 2 in series. The first one should have coarse sand like .65 mm effective size, and the second one much finer sand like .15 mm effective size.