New Developments In Pond Filtration
(Excerpts from an article by B.W. Channing, Japanese Water Gardens)
The Need for Biological Filtration If we had a horse ranch on 100 acres, while walking on the grounds you would have to watch where you step because you might step into something soft left by a horse. If, however, you placed 100 horses in your backyard, you couldn’t step anywhere safely. This condition will also create a serious health problem for the horses and anyone else nearby. In order to alleviate this condition we would need to have a strict policy with regard to cleaning and feeding of the animals.
With regard to Koi keeping the problem is more critical since we as the pond and koi keepers also control the whole environment. Fish essentially breath the very water they swim in, consequently not only do we need a system that takes care of the waste, but we need to convert the harmful chemicals dissolved in the water into relatively harmless ones.
The Method - Biological Filtration
The Nitrite Cycle Biological filters operate on the principal of the Nitrite Cycle and work by the action of good bacteria on the chemicals and harmful bacteria produced by Koi in the natural process of feeding and excreting. These good bacteria are called aerobic bacteria, meaning that they only exist in an oxygen rich environment. There are two different strains of bacteria that consume the harmful chemicals produced by Koi waste and the decay of plants and uneaten food. Once we begin feeding the fish a build up of ammonia will occur as a result of the natural excretion process. We all know ammonia is deadly to fish. As a result of the ammonia build up the pond will become colonized by nitrosomonas bacteria, assuming there is sufficient surface area this bacteria will begin to convert the ammonia into nitrite. While nitrites are not as deadly as ammonia they can also kill in sufficient amounts. Nature is truly marvelous, because at this point, a second bacteria develops called nitrobacter. This bacteria has the ability to consume the nitrite and convert it into nitrates which are relatively harmless and are utilized by plant life. This process is called the "nitrite cycle".
To a new Koi keeper, the word filter will often give the wrong impression. They believe the purpose of the filter is to remove the dirt and solid matter from ponds. Actually the purpose, as stated before, is to convert harmful chemicals into harmless chemicals. The solid matter is the greatest problem when it comes to effective filtration. If you fill any container with any variety of media, such as sand, stone, plastic, hair rollers, matting, sintered glass, etc. in effect almost any inert product, and then flow water containing a high level of dissolved oxygen over it, bacteria will colonise the surface area of the material. The problem is that unless we take steps to seperate the solid matter from the aerated water, the filter chamber will quickly become blocked or begin to accumulate a large volume of decaying material. This will then require cleaning. As we all know the pure action of cleaning the media will effectively destroy a portion of the bacteria that has cultured or colonized. Now consider that it takes 12 to 16 weeks to pass through the nitrite cycle and up to two years to reach maximum efficiency, it is easy to understand that any disturbance to the biological chambers of a filter is completely counter productive.
The ideal situation would be if we could create a biological filter that never needs to be disturbed, thereby creating a stable effective means of treating the water. You may ask, is this is possible? It is now!
In most larger and newly constructed koi ponds the filter should be fed directly form the bottom drain. The reason for this is that the worst water and the greatest amount of solids are in the bottom of the pond. The water then flows to a chamber designed in such a way as to rotate the water forcing the heavier solids to fall the the bottom of the chamber, thereby making it easy to discharge the waste from the bottom drain. Thereafter, the water moves to a second chamber that will mechanically remove the bulk of the remaining solids then the third chamber will remove the balance, then the water entering the biological chamber is clean and will rum indefinitely with little or no maintenance. This is referred to as "Protective Chamber Filtration". There are many different types of biological filtration, but by developing a simple and efficient design we can reduce the maintenance and increase the efficiency of what is basically the life blood of our pond.
Protective Chamber Filtration
This basically mains protecting the biological chambers from contamination by suspended solids. If we can prevent solid matter from entering the biological chambers we then create a situation where those chambers never require any maintenance, thus ensuring that the bed of bacteria remains at the maximum levels at all times. It is only practical to protect the biological chamber if we down-flow the water through the biological media. (See Diagram below) In these modern Four Chamber Systems the whole purpose of the first three chambers is to remove the maximum amounts of solids and to oxygenate the water by forcing it to fall and rise in each chamber before it reaches the biological media within the last chamber. (See Diagram below)
Chamber Number One: Solids falling to the bottom as a result of rotating water.
Chamber Number Two: Further solids trapped by the packed chamber of brushes.
Chamber Number Three: Finer solids trapped by the large blocks of reticulated foam or Japanese Mat Material.
Final Chamber: The media is protected and completely covered by three sheets of reticulated foam.
Protective Chamber Filtration has been used successfully for many years. While regular discharging of the vortex chamber is necessary, the second chamber of brushes only requires cleaning approximately twice a year and the same is true of the third chamber. Also, the reticulated foam in the last chamber may require cleaning twice a year, however the biological portion, (the aqua rock) will remain clean and without build up of solids for years.
The Protective Chamber principal of filtration is simply efficient - efficiently simple.