Pond designs vary in many ways so it is important to use the most efficient filter for the specific pond in question. Pond inhabitants such as goldfish and Koi Carp will also place biological load on the pond, compared to a purely ornamental pond with no fish stock, so filtration needs to be scaled up to cope with this extra load.
As a general rule, a pond which contains small goldfish, shubunkins, Orfe, Comets or Rudd will put twice the strain on fish pond filters compared to no stock. A pond stocked with Koi Carp will need 4 times the filtration capacity to an ornamental pond with no fish.
Almost all OASE Pond Filters are named by the water volume of the pond they can cope with, based on no fish being in the pond. So, for example, the FiltoClear 30000 Pressurised Filter can cope with a pond of up to 30,000 Litres with no fish, 15,000 Litres with small hardy fish or 7,500 Litres with Koi Carp.
The most crucial factors in selecting the right filter for your pond are – how much water do I have and, what (if any) fish will I be keeping? There are other factors to also consider, such as sunlight exposure and water depth (i.e. if you have a very shallow pond in full sunlight, the filter should be upgraded to help combat algae growth due to warmer water temperatures).
To calculate the pond volume, simply measure the maximum length, width and depth in metres and multiply these together, then multiply by 1000 to determine the volume in litres. For example: L2.0 metres x W1.5 metres x D1.0 metres x 1000 = 3000 Litres. Water Garden supply complete packaged filter sets which include pump and UV clarifier, but many of these filters are available on their own, so are ideal if you already have a pond pump and/or an Ultraviolet Clarifier.
A golden rule to remember; you cannot ‘over-filter’ a pond but you can certainly ‘under-filter’ it! Having a filtration system which is more than capable of dealing with the pond and its inhabitants is far better long term than a system which is just on the cusp of its limits.
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