| A filter will also provide oxygen for your pond, | | | | construction, they are far more effective and |
| fish in poorly oxygenated water will become | | | | maintainable. Draining debris is simple and analyzing |
| stressed and die. Adequate filtration cannot be | | | | water quality and condition is effortless. External |
| achieved by the small foam prefilter placed on the | | | | filters fall into two main groups, those which are |
| intake of a pump (this is there mainly to protect | | | | pump fed and those fed by gravity. |
| the pump). | | | | Pump-fed single-chamber filter units are the most |
| Koi are large, active fish that produce large | | | | widely used. They can be installed in minutes, |
| amounts of waste and use up lots of oxygen. | | | | even on an existing pond. There are easy to find |
| Pond fish are just like any other animal in that | | | | in commercial pond shops, even for a large 2,000 |
| they excrete waste that will be toxic if left to | | | | gallon pond. |
| accumulate in their bodies. That is the function of | | | | Gravity-fed multichamber filters are constructed |
| a pond filter; to reduce the deadly ammonia from | | | | or installed at the same physical level as the pond |
| the waste your Koi produces. Ideally your pump | | | | so that the water level in both is identical. |
| and filter need to process the total volume of the | | | | Therefore, if water is drawn from one end of the |
| pond at least once every two hours. Remember, | | | | filter, gravity carries a fresh supply to the filter. |
| do not switch off your filter for more than 12 | | | | Irrespective of how many chambers are used, |
| hours or the oxygen-dependent nitrifying bacteria | | | | water will flow from chamber to chamber, passing |
| will start to die. | | | | through successive blocks of media as it |
| Garden Pond Filter Options | | | | progresses. Water is transferred from chamber |
| For a small garden pond an internal filter will sit | | | | to chamber via transfer ports, and these must be |
| inside of your pond. The internal filter will generally | | | | of sufficient size to ensure there is no restriction |
| consist of large foam blocks that replace the | | | | of flow. This is an excellent filter system but it is |
| pumps strainer. When first matured, this type of | | | | relatively expensive unless you can design your |
| filter is undoubtedly very efficient, but it suffers | | | | own. |
| from the inevitable drawback of area blocking | | | | Pressurized filters are totally sealed and can be |
| caused by a build-up of heavy solid waste | | | | buried, with the return consisting of tubing feeding |
| products and the formation of colonies of | | | | directly into the pond or through a waterfall. This |
| anaerobic bacteria. | | | | makes pressure filters sympathetic to the natural |
| External filters consist of an external chamber | | | | look. They are a small size, tend to block quickly, |
| placed outside of the pond. Although external | | | | and need regular maintenance. They are suited to |
| filtration systems are considerably more | | | | smaller ponds. |
| expensive to build and more complicated in their | | | | |