The main purpose of a biological pond filter in any fish pond is to remove ammonia, which can be very toxic to fish in a pond and other water bodies. The biological process responsible for the removal of ammonia is known as the nitrification process and is extremely important if you want to maintain a healthy ecosystem suitable for aquatic life to thrive. The secondary function of the biofilter is the mechanical separation of leaves and other organic matter from the pond water. I wrote this article in the hope that it would help to underline the failure, in my opinion, of using a mechanical sand filter in any garden pond.
Why are sand filters poorly suited for garden pond?
Before discussing my reasons for which I believe that this filter system has no place in the garden pond, I would very much like to add that I mean a mechanical sand filter, and not a fluidized sand filter intended for use in a pond. Ammonia is present in all fish ponds where there is biological activity, such as feeding fish, decaying vegetation and decaying aquatic life. It is important to remove this toxic chemical as soon as possible.
In order for the conversion of ammonia to nitrite, and then to nitrate, it is necessary to fulfill certain criteria: it is necessary to provide an abundant supply of oxygen flowing through the bioresources of the pond; a large colony of Nitrosomonas and the beneficial bacterium Nitrobacter must be present, and there must be turbulence that mixes water, oxygen and ammonia to accelerate the decomposition of ammonia.
Disadvantages of the mechanical sand filter:
* It has only a small surface area on which nitrifying bacteria can colonize.
* This type of filtration system stimulates the accumulation of unwanted heterotrophic bacteria, which is bad for the quality of water in the pond, unlike nitrifying bacteria, which is necessary. If you allow the development of heterotrophic bacteria in your pond, you will see some unpleasant results, including the production of hydrogen sulphide (rotten smell of eggs), ammonia and carbon dioxide. Think about it! We use a sand filter to remove ammonia, but in fact it produces ammonia.
* Sand filter is expensive because it needs to be washed again 5 to 6 times a day for at least 5 minutes each time. This requires a lot of water, which means that if you are on the meter, it can be quite expensive.
* As water flows through the biomaterials with sand, drainage begins. A channel (holes in the sand) allows water to flow straight through the sand without filtering. This requires even more washing.
What type of pond biological filter should I use?
As far as I know, the only effective solution for effective pond filtration is to use a biofilter or a filter for vegetables, although a veggie filter may be a higher content. If you have a small and medium-sized fish pond, then a biological pressure filter is a really good choice for the following reasons:
* It is compact and easily hidden from view, not allowing it to cool off a bit. Traditional black box filters are bigger and harder to hide.
* Biopolymers under pressure have an integrated backwash system that makes it easy to remove unwanted organic waste such as trap leaves and grass. This simplifies routine cleaning.
* Pressure operation means that this type of filter can be located far from the edge of the pond, and not at the highest point of the pond, unlike the box-type filter, which refers to gravity. My recommendation would be to use either Oase Filtoclear, Hozelock Bioforce, or Fishmate Powerclez, mainly because of their cost, reliability and excellent warranties.
For large Koi ponds, the best form of biological pond filtration is the bead filter or Koi vortex filter. Ball filters contain up to 600,000 balls per cubic foot. This means that there is an extremely high surface area on which beneficial nitrifying bacteria can colonize. These beads are suspended in a turbulent chamber with water, which is constantly filled with oxygen and ammonia. This provides optimal conditions for the destruction of ammonia. A swirl filter is the preferred choice for many professional Koi custodians, as it does not require maintenance and has been tested and verified over many years.
The 2 equivalents below show the amount of oxygen needed to nitrify bacteria to oxidize ammonia (oxygen is represented by O2). As you can see, it is needed in abundance.
* For nitrosomones: 55NH4 + + 76O2 + 109HCO3 - ---> C5H7O2N + 54NO2- + 57H2O + 104H2CO3
* For Nitrobacter: 400NO2- + NH4 + + 4H2CO3 + HCO3- + 195O2 ---> C5H7O2N + 3H2O + 400NO3-
To complete this article, I would seriously advise you not to install a mechanical sand filter in your garden pond. If you are currently using this type of filter, remove it and replace it with a biological filter that will purify the water and not contaminate it.
