Learn All About Fish Pond Filters & Pond Water Quality Part 2 of 4

Shape of a biofilter (pond filter) does not matter. Make your own

Once you fully understand what a pond filter does and how a biofilter (pond filter) works it is simple to buy the right one and it will cost you very little ... avoid being overcharged ... and will make a dramatic difference to your pond water quality and thus the health of the fish in your pond

At their simplest pond filters or biofilter (pond filter) are literally black or green boxes square or round, fat and thin or whatever. Often they hold sponges, brushes or other means of trapping solid particles. The boxes also contain plastic tubing often called Flocor, plastic balls, other weird plastic shapes, lava rock, special tape, string bags and coke bottle tops. If you are lucky the boxes contain Alfagrog. The collective name for these objects is biomedia ie a medium (better still surface) on which biological activity can take place

A biofilter (pond filter) always work best and your pond benefits most from combining the action of ultra violet light (UV) with that of biofiltration ... in this way your pond ALWAYS stays clean and clear and healthy ... no more need to add anything at all to your pond water.

The picture below the table is of a brush that would often be used to trap solids in the circulating water.

Bacteria of a special naturally occurring type are the secret to effective pond filtration

The more bacteria you have in any pond filter the better your pond water quality will be. These bacteria transform toxic chemicals in the pond water secreted by the fish into plant fertilizer suitable for pond plants

For any biofilter (pond filter) to work well the following is needed:

• Reasonably good mechanical filtration (solids removal) before the water enters the biological chamber in the biofilter (pond filter). The better the removal of solids the better the biofilter (pond filter) will work. A large colony of specific bacteria that literally eat the waste products from the fish. The bacteria convert this waste to nitrate chemicals, which act as a kind of fertiliser for plants growing in the pond. The larger the colony of bacteria the more quickly they can destroy waste build-up.

• A continuous supply of oxygen to enable the bacteria in the filter to live. This is why a pump must work 24 hours per day since the water is the source of oxygen for the bacteria and without the oxygen the bacteria die quickly and certainly within 8 hours. Once dead the colony takes 4 to 6 weeks to build up to a reasonable working level again.

• Good water flow rate throughout the filter biomedia. And not just through portions of the bed easier said than done by the way so biofilter (pond filter) tend to be over-designed to compensate.

For effective total filtration of a pond the mechanical aspect of solids removal also have to be good.

Good Pond Filter Design Principles

Later in this book a more advanced but simplified way of viewing factors affecting good filtration is discussed.

A filter will do a good job if there is a way removing solids effectively and of colonising large surface areas of bacteria that are able to intimately contact the water containing the waste products pumped through the system and if there is continuous flow of oxygenated water through the biofilter (pond filter) we tend to use the word filter as a short version of biofilter (pond filter).

The more surface area that can be incorporated into a filter the better. An attempt (albeit a basic attempt) to achieve this is by placing hollow tubes of rough plastic inside the filter box. Other attempts include the use of orange bags, lava rock, tubes, and even hair curlers.

Next pond filter chapter

"The Complete Pond Solver" by Tony Roocroft  Essential reading for anybody who wants or has a garden pond. Get 12 Excel pond calculators free as well as "Water Lilies and Pond Aquatics" ebook also free. THis page is an extract form this book