The major purpose of a biological pond filter in any garden pond is to remove toxic ammonia, which has a detrimental effect upon the pond water quality and pond inhabitants. The biological process responsible for removing ammonia is known as the Nitrogen Cycle and is vital to any biological pond. The secondary function of a pond filter is to remove organic solids such as leaves and uneaten fish food etc.
Why Are Sand Filters Bad For Fish Ponds?
The reasoning behind using a pond filter in the first place is to remove ammonia from your garden pond before it creates a toxic environment that is unsuitable for aquatic life. Mechanical sand filters encourage the growth of heterotrophic bacteria, which paradoxically produce ammonia as part of their metabolism. Heterotrophic bacteria pollute your pond water and will eventually destroy your Koi and goldfish population.
- Sand filters require frequent backwashes; about 6 a day for about 5 minutes each time. This consumes a lot of water. Expensive if you are on a meter.
- A sand filter has a low surface area on which nitrifying bacteria can colonize.
- A sand filter is only capable of trapping solids in water that measure at least 10 microns in diameter or more; algae cells can be as little as 4 microns, meaning that they would simply pass through the sand without being trapped.
- As water flows through the sand channelling starts to occur. This means that holes appear in the sand and water simply flows through, without being filtered.
As far as I am concerned the only viable solution for effective biological pond filtration in a garden pond containing fish is to use a biological pond filter or a veggie filter.
What Type Of Biological Pond Filter Should I Use?If you have a small to medium sized garden pond then the best choice would be a pressurized pond biofilter such as the Hozelock Bioforce, Fishmate Powerclenz or the Oase Filtoclear. They are reliable, energy efficient and come with good warranties.
For large Koi ponds the best form of biological pond filter is a bead filter (fluidized bed filter). Bead filters as the name suggests use tiny little beads suspended in water as the filter media. In certain models there can be as many as 600,000 beads per cubic foot. The turbulent oxygen rich water, ammonia and large surface area provided by the beads ensure that ammonia is quickly converted into nitrate.
My advice to you would be to avoid installing a sand filter in your garden pond at all costs; partly due to running cost implications but mainly because of the unhealthy environment it will create.
The full article can be read at http://www.garden-pond-filters.com/garden-pond-sandfilters.htm, where you will find other water gardening articles and pond keeping resources.
