ProLine® 05040 P-4000 Pressurized Filter System 4000 gal. The ProLine® Pressurized Filter System features a unique, manually operated agitator that quickly dislodges waste from the filter chamber which allows you to backwash and rinse the filter in seconds without getting wet or coming in contact with fish and plant waste. Best of all, these filters never need opening! Available with or without an internally mounted UV Clarifier that controls green water algae