Filtration is essential for the health and well-being of your koi fish. Did you know there is more than one type of filter system for ponds? Combining a mechanical pond filter with biological filtration is a surefire way to keep the water clean and balanced. Learn how each filter option works and how to choose the right equipment for your pond below.
Biological Pond Filtration
Pond filtration is more than just removing visible debris from the water. At a microscopic level, pollutants like harmful microbes and toxic compounds make a pond unsuitable or even dangerous for aquatic life. Biological pond filtration eliminates contaminants you cannot see, leaving you with a thriving and balanced pond ecosystem.
Pond biofilters work by providing surfaces for nitrifying beneficial bacteria to grow and reproduce. These are often mats, sponges, volcanic stones, or other dense media with porous surfaces dotted with nooks and crannies where good bacteria can congregate.
A robust population of pond-cleaning bacteria purifies the water by outcompeting harmful microbes and eliminating pollutants through nitrification. Decaying debris and fish waste release highly toxic ammonia into pond water, which builds up and can kill fish. Nitrifying bacteria break ammonia down into nitrites and then convert nitrites into nitrates. Pond-purifying aquatic plants consume these nitrates as they grow and flourish.
Mechanical Pond Filtration Systems
Mechanical filtration removes excess debris and waste from the water, making biological filters more effective. Pond filtration systems are available in many varieties, including skimmers, pressurized external filters, submersible pond filters, gravity-fed water filters, and more. These units sometimes contain chambers packed with pond filter media, thus combining mechanical and biological filtration in one product.
Additional Pond Filtration Options
The most popular supplemental pond filtering solutions include flocculant filtration and UVC pond filters. Flocculant filters like activated charcoal and natural water clarifiers neutralize harmful substances, rendering them inert and often pulling them out of the water column. UVC—ultraviolet clarifier—filters use high-intensity UV lights to destroy the DNA of nuisance microbes so they cannot thrive or reproduce.
Choosing the Best Pond Filter
The best filter for your pond will likely combine mechanical and biological filtration with a UV clarifier for optimal results. Do you need help choosing a new pond filtration system? Contact us online or call us today at 866-POND-HELP for insightful advice from experienced pond experts.
Read more about pond filters in these handy guides:
Should I use multiple types of filter media?
Pond Filtration System Upgrade Options
Last Updated: February 6, 2025