Filter screen assembly used for the 100-L tank design. (A) External view of the assembly showing both of the interchangeable filter screens in place covered with nylon mesh and the air ring that creates an air curtain over the filter screen. (B) Cross-section of assembly showing the central standpipe and the base assembly, with a ø90 mm PVC end cap glued into a ø100 mm PVC end cap, in which the filter screens fit.