Efficient Biofiltration biologically and mechanically cleans pond water ClearChoice® Biofilter sponges remove suspended matter from the pond. A combination of Trickle-Flow Technology, aeration and massive surface area promote the growth of ammonia-consuming bacteria. TetraPond® ClearChoice® Biofilters make it easy to maintain the health of your pond. Three models can handle small, medium and large ponds, up to 2,400 gallons. Connected in parallel, they can even clarify extra-large water gardens or Koi ponds. Model Cleans ponds up to Overall Height PF-1 1200 gal. 12.5″ PF-2 1800 gal. 17.5″