There is a simple fact of nature - for every gramme of food (calories) you put into a pond, a corresponding amount must either be absorbed by the pond's inhabitants - fish or plants - or a corresponding amount removed.
Depending on temperature and temperament, fish use approximately 60% of the energy available in commercial pond food. This then leaves approximately 40% to feed the green water or Blanketweed and the other aquatic plants.
Fish as poilikotherms do not need food to maintain a body temperature.
More than two-thirds of the food we consume is used to maintain our body temperature, fish simply do not need this, but it is very difficult to convince people to stop overfeeding, therefore other means have to be employed to remove the excess food. This is where filtration comes in.
There are two basic types of filtration - Particle Removal and Biological Conversion. So how large a filter do you need?
A Particle Filter should be approximately 10% of the pond's volume.
A Biological Filter approximately 20% of the pond's volume.
In general, filters containers are based on the black uPVC plastic water storage tanks found in most lofts, ranging in size from 45l/10gall to 227l/50gall.
Filter systems come as single units or in multiples according to the amount of water to be treated.
External filter containers in the majority of situations will require hiding or camouflaging either by building a rockery around them using the earth dug out for the pond, or by installing them in an adjacent garden shed.
For the small pond there are available submerged filters; some thought must be given to their positioning in the pond as they will require the usual maintenance.
A unit manufactured by Rolf C. Hagen is shown below.
By using two sponge chambers (1)
the filter reduces maintenance.
Water enters the two sponge chambers, the one nearest to the pump inlet (2) having initially the least resistance will clog first forcing more water through the rear sponge chamber until that too clogs; the sponges must then be removed and washed clean of filtered material.
The Biomax chamber (3) contains the medium on that is colonized by a Zoogoeal Film. This should not be disturbed and must not be allowed to
Initially periodic checks must be made on the sponge chambers to ascertain how long it takes for the sponge chambers to clog.
© FBAS 2004 RCM/RDE Pond Care Sheet 4 1/3