Garden Pond Filter Shape and Size Does Not Matter
What is The Optimum Shape and Size for a Garden Pond Filter?
To be perfectly honest the shape of the biological filter does not matter, as this is not the deciding factor that dictates how effective the filter will be at removing ammonia and purifying pond water. From an aesthetics point of view maybe a nice green filter with a red lid looks attractive but will it do the job you want it to? Only time will tell I guess! The same applies to the size of the filter. Yet again it is not a deciding factor; it is the choice of pond filter media that is critically important here. A biological pond filter is a convenient place where oxygenated water, ammonia and nitrification bacteria (Nitrosomonas and Nitrobacter) meet and allow the Nitrogen Cycle to take place.
The Nitrogen cycle, also known as the Nitrification process oxidizes toxic ammonia into much less harmful nitrate and continues to take place in the pond filter chamber whilst there is a constant supply of ammonia and oxygen rich pond water to feed the nitrifying bacteria who live there
Click here for unbeatable money saving offers on USA Pond Supplies and Pond Keeping Equipment in the UK, Guaranteed.
The picture below is courtesy of Peter J May and shows a typical black box garden pond filter. This pond filter design is still used extensively by pond keepers worldwide and is cheap to buy, proven and easily upgraded.
You will notice that water is pumped into the filter box at the top where the pond water containing ammonia and other solids passes through a series of mechanical filter brushes. These brushes are designed to trap leaves, grass and other large solids before they have a chance to interfere with the beneficial nitrifying bacteria.
The water flows down to the bottom of the filter box and rises upwards through the biological filter. Up flow filters i.e. those that allow oxygenated pond water to flow up through the pond filter media encourage ammonia to mix with oxygen and nitrifying bacteria and are a good design principle.
The space at the bottom of the filter box is to allow waste matter to accumulate. This can be drained form the filter via the purge valve. It is important to that you remove this organic matter frequently as it contains heterotrophic bacteria that will affect pond water quality and cause fish health problems.
The top layer of blue open cell foam traps organic matter that managed to escape the clutches of the filter brushes. This open cell biomedia foam also provides a further surface on which nitrifying bacteria can colonize. The Nitrosomonas and Nitrobacter beneficial bacteria live in the tiny holes in the matting and any other available surface within the biofilter chamber.
You will notice that water is sprayed onto the filter brushes. This helps to create turbulence by adding oxygen into the pond filter. Turbulence is important and is covered in the interaction between nitrifying bacteria and oxygen on this site.
Remember that the nitrifying bacteria need to be supplied with a constant supply of oxygen on a continuous basis. If you want to save yourself some money then ensure that you use an energy efficient pond pump model as it will need to run 24/7.
Good Pond Bio Filter Design Principles
There must be a way to allow large colonies of bacteria to colonize. The choice of biomedia is important. Use a biomedia with a large SSA (specific surface area) as this increases the biomass (size of bacteria colony).
Tip: If you currently use plastic bio media as the home for colonies of nitrifying bacteria to live on then I would advise you to replace it with Supra pond filter media the best biomedia for small to medium sized garden ponds. The Nitrogen cycle responsible for the conversion of ammonia relies on nitrifying bacteria to oxidize the ammonia into nitrite and then into nitrate. The higher the surface area for them to live on the larger the biomass (the number of bacteria) there will be. The more bacteria there are the greater the amount of ammonia that can be broken down in one go, providing of course that there is an adequate supply of Oxygen which is essential for the nitrogen cycle to take place.
Ideally a system that allows organic waste to be removed before it has a chance to enter the biological chamber is ideal. One such system is a vortex koi filter which is the professional koi keepers favourite in the UK. In the USA the Koi keeping community tends to lean towards bead filter systems such as those from GC Tek and Fluidart which also offer outstanding large scale koi pond filtration. If you only have a small to medium sized pond then a box type pond filter, as in the diagram above or a pressurized pond bio filter are great alternatives.
Click here for unbeatable money saving offers on USA Pond Supplies and Pond Keeping Equipment in the UK, Guaranteed.