Why You Need Filtration

A biological filter is the most common way of keeping a fish pond clean and healthy for your fish. Ponds without filters are usually green and not pleasing to the eye. It is possible to create a clear pond with the use of water plants which add oxygen to the water, however most pond owners find this system unsuccessful and have problems with plants removing oxygen from the water during night time hours. A biological filter is the way to solve the green water problem.

The principle behind biological filtration is very simple. A pond naturally creates a bacterial growth as it establishes its eco system. This bacterium is the principal destroyer of algae. By fitting a biological filter of the correct size to your pond you are supplying the bacteria with a home in which to develop, grow and go about its job of clearing algae growth. Under normal circumstances it will take 4-6 weeks for bacteria to colonize in the filter and begin the cleaning process. The addition of PondMate or Sol Bio Booster will reduce this delay. Addition of the same bacteria at regular intervals will also enhance water clarity. The size of the required filter is determined by the size of your pond and the number and type of fish in the pond. In general, the larger the pond the larger the filter required. The higher number of fish the larger the filter. The surface area of the filter media will also determine the physical size of the filter box required.

Equipment sizing – Calculating Pond Size

Volume: Average width x average depth in metres x 1000 = Litres

Example: 3m wide x 2m long x 1m deep = 6000 Litres

Calculate Effective Volume of your Pond Factor

Average pond depth less than 0.75m. Influences pond area which affects intensity of sunlight 25%

Pond located in full sun 25%

Climate – Hot Climate 35%

Example: You must calculate the effective volume by selecting which of the above condition factors are applicable.

For a 6000 litre pond 600mm deep exposed to full sun (Australia) you would need to add (25%+25%=35%) giving a pond as if it were 12600 Litres.

"It is essential to realize that the flow of the water through the filter must be kept constant so you must run your pond pump continually. If the water flow stops for too long the bacteria growing in the filter will die and the process must then start over. (Hint: check the running cost of your pump). Most pumps are rated for continual running and are not expensive to run. As a rough guide each watt of motor power will cost about $1.00 per annum if operated continually.

When topping up your pond it is best to add a little tap water at a time (say 10% of pond volume) rather than a lot at once. Again the chemicals in the water may harm bacteria. If you find it necessary to use chemical additives in your pond, check if they will be harmful to bacteria.
If you want clear and little maintenance, it may be worth looking at a ultra-violet clarifier, particularly if you intend to keep Koi.

Cleaning of your filter is required from time to time depending on a number of factors: sunlight, type of fish, number of fish etc. It is essential that you do not use tap water when cleaning it because the chemicals which are added to drinking water for protection will harm or kill the beneficial bacteria in your filter. For this reason it is best to take a bucket of water from the pond and gently wash the filter media. Discard this water into your garden.

* Watch out for more filters coming soon!