In my usual web surfing I came across a couple of discussions about Rotary Drum filters. A RDF is primarily a mechanical filter that uses a rotating screen to remove small and large particles from the water as it passes through the screen. Water is pumped to the center of a screened drum and debris sticks to the screen. As the drum rotates it passes over a waterjet which cleans the screen and knocks the sludge/debris into a tray that then drains out of the filter. The filtered water passes through the screen onto then next filter via gravity flow.
The RDF will usually have a sensing device that can tell when the screen is full and will start the rotation automatically. There is very minimal water loss and the debris is removed from the water column so it doesn’t contribute to ammonia build up. Due to all the moving parts, motors, sensors, and fine screens the RDF units are very expensive, $2500+ (USD). While they drastically reduce maintenance on the pond, the units themselves require some maintenance. Some people have created DIY versions of them but I have yet to see one with all the automated functions of the commercial models.
This is one of those items that is a nice to have, and if you are mechanically inclined would be an easy addition to any pond setup. RDFs work far more efficiently than other screen methods and can be sized to meet large water flows. If you have the budget, do the research and find units that meet your need.
