Biosteps 10 Progressive Filters Biosteps 10 w/13W UV Clarifier by Matala. $349.99. Matala biological filter for koi ponds and water gardens Expandable, high-capacity pond filter accommodates a variety of ponds Provides unparalleled biological filtration for superior pond water quality Expandable gravity filter maximizes Matala filter media performance. The rugged Biosteps 10 contains an amazing 200 sq. ft. of surface area for beneficial bacteria growth. Combined with a cross flo...