The Ultima II Bio-Mechanical Filters by Aqua Ultraviolet are excellent choices for large aquarium systems. The various sizes are designed to handle systems from 1,000 gallons to 60,000 gallons. They can handle high flow rates, heavy fish loads, and require only minutes to backwash. The bio-media is of a unique tubular design the protects beneficial bacteria while dislodging debris. The entire compact filter can be buried up to the valve to save space.
These filters provide both mechanical and biological filtration. Backwashing should be done at least once a week to remove accumulated waste. It should be done more often for heavier waste loads. Backwashing is easily accomplished by simply depressing and rotating the valve handle. Filters with 1.5" valves are designed to handle flow rates up to 75 gallons per minute. The 2" valve models can handle flow rates up to 125 gallons per minute.
This model 20,000 has a 2" valve (flow rate up to 125 gallons per minute), is designed to handle ponds up to 20000 gallons in size, and measures 31" in diameter and 50" tall. It includes 7 boxes of media.