Your Pond Does Need A Bio-Filter or Your Fish Will Die
The vital importance of good water quality in a fish pond just like you and I thrive on fresh air, pond fish thrive in clean pond water.
Generally speaking a garden pond has too many fish for its own good. In a garden pond fish consume food and excrete waste products continuously as part of their normal metabolic process. The waste products build up in the water unless they are continuously removed. In simple terms the pond water is also the toilet water.
Clean pond water is water that has been purified by removal of the waste products. It may not be clear, but can still be clean.
Many readers will have had a goldfish in a bowl at some stage. They almost certainly noticed that the fish died after about a week but the reason was never known. Well, in all likelihood the poor goldfish had poisoned itself to death.
The waste products produced by fish consist essentially of nitrogen chemicals and the most important one from the perspective of good water quality is mainly ammonia. This chemical is poisonous in even small quantities.
The amount of waste products such as ammonia in a pond is dependent mainly upon two factors
1. How many fish are in the pond and what size the fish are the bigger the fish the greater the amount of waste produced
2. How much food is fed to the fish and how frequently this is done. In general people over-feed their pond fish. It is always better to feed little and often than lots once per day for example. Bear in mind also that koi produce 3 times more waste than goldfish of the same size - because they eat 3 times more.
The food used to feed your fish has a significant impact upon the amount of waste produced. Do not use foods with high ash contents - this indicates low quality raw materials have been used in the food manufacturing process.
If pond water is changed frequently then to some extent the poison levels are controlled. However this is not only a hassle but it is real cost and unnecessary if a biofilter is installed in the pond water circuit.
In a natural stream or lake
Fish concentrations are generally low. Waste products are converted to relatively harmless nitrates by naturally occurring bacteria. Rocks, submerged trees, etc all help to purify the waste products from the fish by providing holding points for the purifying bacteria to live on. The more bacteria there are the better the purification.
The bacteria need oxygen to survive and they get this from the water - oxygen is absorbed by the water through the action of waves, waterfalls and wind
In a garden pond
A biofilter is installed to make up for the unnatural conditions prevailing. A biofilter is designed to allow large concentrations of bacteria to operate effectively in a small area within a garden pond environment. When correctly specified and installed biofilters create very healthy environments in which fish can live and grow to their full potential.
The biofilter is best installed outside of the pond. The pump connected to a biofilter must run 24 hours every day otherwise the bacteria inside the biofilter which are doing the water purification will die from lack of oxygen contained in the circulating water. It is not just the fish that need oxygen.
It is always a good idea to have a waterfall or a fountain to increase the oxygen content of the water. Once the bacteria in a biofilter have died it will take approximately 5 more weeks for them to get back to their previous levels.
Learn more about biofiltration here http://www.clean-garden-ponds.com
Do not believe the stories about how big a biofilter must be. Many people will say it must be 1/3rd the size of the pond which is frankly ridiculous. The size of the biofilter is governed by the biomedium used and the overall system.