I say there really is no set-in-stone time when you must clean your filter. It really all depends on what the filter pad’s purpose is.
Biological filter media really shouldn’t be cleaned that often. This is because, unlike mechanical filters, bio-filters contain bacteria that work on a microscopic level to “eat” pollutants. You generally want to let them do their thing if you can. Only worry about cleaning your pond’s biological filter every few months if you are experiencing a decrease in performance.
If your filter media is being used as part of your biological filtration system, then you do not want to use tap water to clean them. Very similar to fish, the bacteria in your bio-filter are used to the chemical balance of your pond, not the tap water. The proper way to clean your biological filter inserts instead is to use pond water. What you do is take a 5-gallon bucket of pond water and take each insert and clean it in that bucket. You will want to give it a good dunk and then squeeze it out. Repeat this process a couple of times and then discard that water in a garden or drainage area. Make sure you do this for each insert. Now if the insert is strictly being used mechanically (to just collect waste), then you can wash it with tap water.
For mechanical filter media, I generally like to rinse them out every 4 – 6 weeks, depending on the load being placed on them. I find it helpful to rinse off my mechanical media with a garden hose on a jet setting. One thing to note, however, is that fine filter media will need to be cleaned more frequently than coarse media. This is because it is densely packed and traps a lot more debris. It will also require a little extra effort to rinse out.
I would also like to mention that if you see a lot of muck in or on your inserts, you may want to consider using a beneficial bacteria additive like Microbe Lift PL or Biosafe Xtreme as this will help aid the beneficial bacteria that is growing on your inserts breakdown organic waste. Lastly, I suggest changing your inserts each pond season with fresh new insert parts from the manufacturer so that you can get the most out of your pond filter.
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