More bacteria in your fish pond filter = cleaner pond water
When it comes to keeping good water quality in your garden pond, you need to have a high level of bacteria in your pond filterThese bacteria transform toxic chemicals in the pond water--secreted by koi and other fish--into a plant fertilizer that's absorbed by plants in your pond. But keep in mind that choosing the correct biomedia will have a major impact on the performance of your biofilter. In order to do its job effectively, a filter needs a way of removing solids and colonizing large surface areas of bacteria. These bacteria in turn contact the water containing the toxic waste products as they are pumped through the pond system. This is why there needs to be a continuous flow of oxygenated water through the filter at all times, or you risk killing the biomedia by starving it of life-giving oxygen. Surface area is an important consideration when designing a pond filter. The more surface area that's available to the biomedia, the better. One way to achieve this is by placing hollow tubes of roughened plastic inside the filter chamber. Other filters accomplish this by using orange bags, lava rocks, tubes, beads, and even hair curlers. Good pond filter design principlesAn important feature of any biofilter is the ability to create holding areas for the bacteria, or biomedia. There needs to be large areas for the bacteria colonies to grow on, which is why many filters are contained in large-sized boxes. Foam sheets provide another way of providing surface area by virtue of their many small holes, where bacteria can grow, as well as acting as a mechanical filter to remove solids. But by far the best method of attaining a large surface area inside a smaller filter box, at low cost, is through the use of porous ceramic materials like "Alfagrog." This is a product manufactured in the UK specifically for fish pond water purification. It has an enormous surface area per volume--between 40 and 100 square metres per liter. This is in contrast to plastic tubes, which might have 0.2 square meters per liter. In simple terms, this means that 1 liter of Alfagrog can contain the same amount of bacteria as 200 liters of plastic tubes. And so a much smaller filter box can do the same work as a larger one. As you can see, Alfagrog is a much more efficient medium in which to colonize bacteria. In the US, Alfagrog is referred to as Supra. For more on this topic, see the bead filter and Supra articles. |
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