Types of UV Pond Filters

Sizes

• It’s very important to install a UV filter large enough to filter all of the water in the pond. Otherwise, it will not help to kill suspended algae. “Zen & The Art of Pond Building” recommends installing a UV filter made for a larger pond than the pond purchaser owns. A pond of 450 to 1,000 gallons large needs a 40 watt UV filter. A pond of 1,000 to 1,500 gallons large needs a 64 watt filter. A pond of 1,500 to 2,500 gallons large needs an 80 watt filter. And a pond of 2,500 to 4,000 gallons large needs a 120 watt filter.

Basic Clarifiers

• A clarifier is the basic type of UV filter without any additional features such as biological filtration. Clarifiers consist of a UV bulb inside a hard plastic sleeve. Sleeves made of Teflon or quartz are better for ponds that are normally colder than 72 degrees Fahrenheit. Replacement sleeves can be sold separately. There are a few openings so that the filter can be attached to the pond’s air pump, which pushes the water over the bulb. This type of UV filter is easy to add to a pond that already has another type of filter, such as mechanical or biological filter, to remove harmful chemicals. This is also better for smaller ponds with suspended algae problems, instead of ponds with filament or “stringy” algae.

Pressurized or All-in-One

• These filters are shaped like canisters. They not only have a UV light source but also contain a biological filter to help remove other harmful chemicals in pond water, such as nitrates, which can cause harmful ammonia spikes. Pressurized or all-in-one filters include an air pump, an item lacking in standard UV clarifiers. Some types will include motors that automatically shut down if the water level becomes too low. Some types may include a fountain pipe so filtered water sprays up in the air in a waterfall. Some types can be used just with the biological filter medium and not any UV light. This type is useful for very large ponds that need more than one filter in order to keep the water healthy.

Other Tips

• All sizes and both types of UV pond filters need their sleeves cleaned on a monthly basis. Remove sleeves and wipe debris away with a clean, dry rag. Any stubborn algae “slime” can be removed with a splash of rubbing alcohol on the rag. UV bulbs need replacing at least once a year.