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How often are you really supposed to wash out your filter? | Decorative Ponds & Water Gardens Q & A

Q: How often are you really supposed to wash out your filter?

Q: How often are you really supposed to wash out your filter?

Al – Greenville, RI

A: The filtration system in your pond is made up of two parts: the mechanical filter and the biological filter. They both clean and clarify the water, but they do so in very different ways and require very different cleaning regimens to keep them optimally operating.

The Mechanical Filter

The skimmer or pump sock make up your mechanical filter. Able to function at all temperatures (as long as the water is liquid), their main purpose is to catch larger debris, like chunks of algae, leaves, foliage and other things that blow into your pond and settle on the water surface. These items are collected in a mat or debris net/basket as the water passes through the mechanical filter, which then protects the pump from clogging.

Cleaning the mechanical filter is easy. You simply remove the mat or debris net/basket, dump out the debris and rinse it with a garden hose. This can be done as often as you like or as needed when you see the water flow slow down. In fact, checking it often is a good idea, particularly in spring and fall when debris tends to collect in a pond.

The Biological Filter

Your waterfall box, pressurized filter and in-pond filter filled with beneficial bacteria-covered filter media make up your biological filter. Their main purpose is to break down tiny, suspended debris, resulting in crystal clear water.

Here’s how it works: Unlike a mechanical filter that physically removes debris, a biological filter works at a microscopic level. Aerobic beneficial bacteria colonize and flourish on the surface area of filter media – like BioBalls™, mats and the like. As the water passes through the filter media, the bacteria feed on the debris and remove it from the water. Because the beneficial bacteria are living microorganisms, they function best when water temperatures are near or above 50 degrees Fahrenheit when they’re alive and kicking.

You don’t really “clean” a biological filter at all because you want to retain as much of the beneficial bacteria as possible. In the early spring, perform a cleanout and seed with natural bacteria like Microbe-Lift® PL Gel or Pond Logic® Seasonal Defense® to give your filter a fresh start. Throughout the season, do a mild rinse in a bucket of pond water only when the water flow begins to decline. Each time to clean or rinse your filter media, add a dose of Microbe-lift® PL Gel or bacteria from the Pond Logic® DefensePAC® to re-seed the bacteria and replenish any bacteria loss.

Though it may be tempting, don’t power wash or swap out filter media mats. This strips the beneficial bacteria, which may take weeks to replenish! In the meantime, algae will feed on the unfiltered nutrients in the pond water, and you’ll see your water quality diminish as fish waste accumulates – which is something you don’t want!

Pond Talk: What’s your mechanical and biological filter cleaning routine?

Promote Healthy Filters - Pond Logic® DefensePAC®

8 Responses

  1. I’ve got a nexus 310 my pond is clear but the nexus is frothing up

  2. I have a mechanical of bio ball and stuff. The water in tank is clear. However algae starts growing in the filter. Can I flush the bio balls with water to get rid of the algae or should I just leave the algae alone?

    • Hi Vincent – It is normal to have some algae growth in the filter as it is feeding on the dead organic material. As long as it is not causing the filter to plug up so water can not pass through I wouldn’t worry about it too much.

  3. Our mat gets so clogged with algae it can actually raise the lid of the filter box. We end up cleaning it frequently, probably once a week in summer. The water appears clear, is there a problem elsewhere is our system? We have a skimmer we clean frequently and a UV light. 4000 gal pond and 40 watt light. Thanks

    • Hi Kin – Just to clarify do you have a filter in addition to the skimmer or is it just the mat in the skimmer box that is being cleaned weekly? The flow rate of the pump if it is too large, in relation to what the filter can handle, may also play a role in the additional pressure building up in the filter.

      • Yes, we have a filter in addition to the skimmer and it is the mat in the filter that has to be cleaned weekly. The mat seems to perform well until the algae builds up on it.

      • If there is room in the filter I would add additional filter media. Also do you add any beneficial bacteria such as Nature’s Defense directly to the pond? The additional bacteria will help to breakdown some of the additional muck in the pond. You can even add some directly to the filter.

  4. I live in Florida, and I clean out my skimmer once a week, last summer when it was really hot the algae grew fast enough that I had to clean it twice a week for a while. I usually don’t clean my bio-filter more than once or twice a year.

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