5 Common Pond Filters And Why You Need Them

There are a few different types of common pond filters and each of them serves a unique purpose. Find the best filter for your pond by matching pond filter with function. 

Here are 5 Common Pond Filters and Why You Need Them:

1. In- Pond Pre-Filters 

In-pond pre-filters (or filter boxes) are designed primarily for small pond setups between 200 and 500 Gallons. They are typically sponge filters that attach to the intake of your pond pump and sit in the middle of your pond.

In-pond pre-filters provide mechanical filtration by removing small particles in the pond water. These filters are quite limited in biological filtration as most have only a small sponge area. A few models do offer additional biological filtration in the form of a bio chamber add-on filled with ceramic or plastic balls, such as Laguna Biospheres. Bio balls improve your pond's biological capacity, but still do not provide enough bio filtration for a pond heavily stocked with fish.

Best Pond Use: Filter boxes have an adequate amount of mechanical filtration for small ponds (under 500 Gallons). These pond filters are not recommended for use with a moderate to heavy stock of fish. If you are running with even a small amount of fish, find a pre-filter with an additional bio-chamber for more effective cleaning.

2. Skimmers

Skimmers can be used in almost any size of pond, from 250 gallons to thousands of gallons. Skimmers are a box mounted at the water level of the pond outside the liner, which also contains your pump.

A skimmer’s primary purpose is to remove the large debris that blows or fall into your pond before it sinks to the bottom to decompose. The skimmer filter works by continually drawing the surface water off the pond. Debris collects continually for easy removal from the pond system. As a bonus, this process also allows for superior oxygenation of the pond water. 

Best Pond Use: Pond skimmers are invaluable in areas with a lot of wind or if there are trees near your pond. However, since skimmers are strictly mechanical in nature, you may need to add additional biological filtration (especially if you are having large numbers of fish in your pond). Skimmers are a highly recommended (and in some cases, indispensable) part of your overall filtration system no matter how large or small your pond. 

3. Pressure Filters

Pond pressure filters are used primarily in small to medium sized ponds (200-5000 gallons). Primarily a mechanical filter, pressure filters work by forcing water through a sponge filter that collects small debris. 

Pressure filters provide a high degree of convenience and flexibility. Being pressurized, pressure filters can be located pretty much anywhere you choose – above the waterline or buried hidden in the ground. 

Is water clarity an issue for you? Many pressure filters have a built in UV sterilizer, which eliminates green algae particles from pond water. Most pressure filters also have a back flush function that allows for exceedingly simple cleaning of the filter sponge and an easy method for doing water changes. 

Best Pond Use: Pressure filters are an ideal option for small to medium sized ponds as they are effective mechanical filters and simplify routine maintenance of your pond. They work well in conjunction with skimmers as they filter smaller debris. If you are keeping fish in your pond, having a simple method of doing regular water changes is a feature that is highly desirable and should not be overlooked.

4. Waterfall Filters

Unlike many pond filters, Waterfall Filters are not under pressure so they need to be located above the water level. Also called gravity return filters, these filters are found in the form of waterfall filter boxes so they can be incorporated into water features.

Waterfall filters consist of some mechanical filtration in the form of layers of sponges. They often have significant amount of biological filter materials in the form of ceramic bio beads, plastic bio balls, or bio mesh.

If you are keeping fish, having adequate biological filtration to eliminate organic toxins such as ammonia and nitrites is a must. These toxins are deadly and can be detrimental to healthy fish keeping.

Best Pond Use: Waterfall filters can be used in any size of pond. Small to medium size (up to 1000 Gallons) ponds tend to benefit the most from the biological component as they tend to be more biologically unstable due to smaller pond surface area. Gravity Return Filters are highly recommended for small or medium size ponds with fish. 

5. UV Sterilizers

While not technically a pond filter, UV Sterilizers perform an important filtering function within the pond. UV Sterilizers or Clarifiers work at the microscopic level to eliminate free-floating organic particulates. This means anything from algae and fungi to harmful viruses and bacteria.

UV Sterilizers work by exposing tiny organic material to high powered UV lights. These lights alter the structure of the organisms at the cellular level.

UV Sterilizers require a pump for water flow, which can either be your main pump teed off or a separate pump designated for the sterilizer. For optimal functioning, you must replace your UV bulb at least every season.

Best Pond Use: UV Sterilizers are useful additions to any pond. If functioning in the correct conditions, UV Sterilizers eliminate green water in small to medium-sized ponds. With the added benefit of destroying waterborne viruses and bacteria, UV Sterilizers are essential for ponds with fish.