How Does A Biological Garden Pond Filter Work?
Pond Filter Media Selection Affects Ammonia Conversion Rate
The performance of a biological pond filter, no matter what size, what shape or what filter media is used will perform according to the processes determined by the nitrogen cycle.
The Nitrogen Cycle In Your Pond
The nitrogen cycle or nitrification process describes how nitrogenous wastes are broken down in nature. In a fish pond it describes how toxic ammonia is converted into nitrite and then into nitrate by the actions of nitrifying Nitrosomonas and Nitrobacter bacteria living in your pond filter. Nitrate is either used up by pond algae to complete their biological cycle, or is released into the air as nitrogen gas. In a fish pond the major contributor to the levels of ammonia found in the water is fish metabolism (food digestion, energy production, tissue repair and cell growth). Other sources of ammonia include rotting fish wastes, undigested fish food and other organic matter.
The Nitrogen Cycle is a very important aspect of pond keeping, as without this natural process taking place any garden pond would quickly become a toxic environment, unsuitable for pond fish to live in.
The rate at which ammonia is converted is dependant upon several factors including the choice of pond filter media used, the level of oxygen in the pond water and level of ammonia that needs to be converted.
Click here for unbeatable money saving offers on USA Pond Supplies and Pond Keeping Equipment in the UK, Guaranteed.
It is important that you try to understand these basics as they will help you to make informed decisions and save you money when purchasing a garden pond filter and more specifically the choice of pond filter media used.
In chemical engineering the factors that determine the conversion rate are determined by the laws that govern “Mass Transfer Processes: "Mass Transfer Processes are defined as: “At the interface between two components transfer between the two is limited by the concentration difference. The larger the concentration difference the faster the transfer will take place.”
In simple terms this means that a large particle has a much smaller surface area per unit of volume than a small particle. In a pond filter this means that if you use a pond filter media with a small surface area then mass transfer will take longer than if you were to use a pond filter media with a much larger surface area. For example if you were to double the surface area on which bacteria can colonize then you half the time in which it would take to break down X amount of ammonia.
In the Koi keeping industry you will see that many of the bio filtration systems used are bead filtration systems. Bead filters utilize techniques to create turbulence, whether that be air blowers that blow oxygen into the water inside the filter or bead agitators that vigorously shake and stir the biological bead media, so as the encourage faster mass transfer rates.
If you have a black box type filter or a pressurized pond filter, then the cheapest and best way for you to significantly improve the rate at which ammonia is broken down is to use Supra biomedia (Alfagrog in the UK), a low cost porous pond filter media that has a large SSA (specific surface area) on which nitrifying bacteria can reside.
Please be aware that the one piece of pond keeping equipment that you don’t want to cut back and save money on is a biological pond filter. If you have a fish pond then you MUST HAVE A POND FILTER. For small to medium sized ponds I would recommend either a box type filter or pressurized pond filter from the likes of Oase, Hozelock and Fishmate. Those pond keepers with large Koi ponds should seriously consider a bead filter system capable of handling large amounts of ammonia and pond water.
Click here for unbeatable money saving offers on USA Pond Supplies and Pond Keeping Equipment in the UK, Guaranteed.