Pond Filters And Fish Ponds

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Written By Mark Washburn

Mark has 20 years of experience as a professional pond management consultant.

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Most people that build a small pond or water garden usually want to add fish into the mix at some point. If you want a backyard fish pond there’s one key tool that you can’t afford to overlook and that’s a good quality pond filter.

Pond filters are one of those things that will play a major role in the daily management of a fish pond. They’ll help any small pond overall but the focus of this article will discuss why they’re essential for ponds with fish.

Many new pond owners may overlook the fact that adding fish will dramatically affect the water quality and balance in a water garden. Namely their waste output creates a build up of potential substances that are toxic to fish. This sounds odd, until one considers that all small ponds are basically contained ecosystems, and while nature has it’s own way of dealing with issues like this, a man-made environment may not.

As waste is released, the substances that make this up are broken down by a process nitrogen cyclecalled the nitrogen cycle. Fish waste and other decomposing organic material is naturally broken down by bacteria which creates a form of ammonia in the water. Ammonia is immediately (hopefully) addressed by nitrite bacteria which turns it into nitrites. It should be noted that both of these substances (ammonia and nitrites) are very toxic to fish if they build up at all in the pond. Therefore it’s best to keep them in check at all times.

Ultimately, nitrates are broken down into harmless nitrates and these actually are consumed by plants. Fish may eat some of the plant material so at this point the cycle is complete.

It’s easy to see that without certain bacteria in the water, much of this process is hampered or slowed down a great deal. Many times when you see unwanted growth like algae in a small pond, part of this process may be working but there is a net result of too many nitrates left in the water. Algae, like any plant, will use this to grow and in doing so, it may help keep the water quality and the nitrogen cycle in some sort of balance for awhile.

There is a certain problem with this however in that as much as a pond owner might want fish, most don’t want an algae bloom, and they certainly would prefer to avoid losing all of their fish to an ammonia spike.

Pond filters take on the pivotal role of keeping all of these elements in check. More specifically, biofilters address a lot of the problem. For example, a koi pond filter will have several components in it. As water flows into the filter, there is usually a mechanical form of filtering, such as using mesh pads to catch the larger particles and debris that may be in the water. Some of the smaller organic material and the very small elements in fish waste will get caught up in the filter as well. These normally end up in what’s called the bio chamber where there is an additional type of filter media that is also home to high concentrates of beneficial microbes. It’s this bacteria that goes to work in cleaning up the unwanted elements in the water. Cleaner and clearer water will exit from the filter and back into the pond.

A pump will drive this flow of water and while manufacturers suggestions may vary a bit, the pond’s entire water gallon volume should turn over many times throughout the day. This ensures constant filtering and regeneration of healthier and cleaner water for the fish to live in.

pond filter graphicYou’ll find biofilters in a variety of designs. Some may to at the head or top of a waterfall system while others can sit externally outside the pond. All of them, regardless of where they go or how they look, function in pretty much the same way.

Various media material (the part that provides a home to the bacteria in the filter) can be used and these might vary from a plastic coil material to scrubby pads, to plastic balls which special chambers in them. All of these help to keep the bacteria protected and in place, even though water and debris may flow through the filter.

Here are some suggestions that may help you maintain a healthier fish pond using a good pond filter.

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