Article 2 - Fish Pond Filters
Fish Pond Filter Types
All water contains impurities, such as ammonia and nitrite, that are
harmful and can kill your fish. Like any other living creature, Fish excrete
urine and produce feces, and ammonia is excreted through the gill membranes.
In the wild, natural ponds handle these impurities by diluting them
in their large volumes of water, or washing them away in the running
water that often feeds ponds. In your backyard, however, you'll need
to have a filter to replace what Mother Nature does herself.
Mechanical filtration
Mechanical filters use a filling, called media, and settlement chambers
to clean and purify the water. Settlement chambers allow gravity to
drag the solid waste out of the water by slowing the water flow. These
chambers usually come first in a filter, pre-treating the water before
sending it through the media to remove the finer particles.
Biological filtration
This filtration method uses specific bacteria to break down toxic waste
products and convert them to inert particles. This process uses a two-stage
approach. The first stage breaks down ammonia to nitrite using nitrifying
bacteria such as Nitrosomonas. The second stage is the conversion of
nitrite to nitrate by Nitrobacter.
Both of these bacteria need oxygen to live. Since sediment building
up in the filter depletes the available oxygen levels, it is important
to keep sediment to a minimum by having a settlement chamber first and
by cleaning the filter out occasionally.
A variety of filter media are available including gravel, matting,
hair rollers, foam, and canterbury spar. They all provide s good surface
for the bacteria to live on. On the down side, a biological filter will
take weeks or even months to mature. You can buy cultures of nitrifying
bacteria to l speed up the process.
Chemical filtration
Am ammonia and other organic waste products are removed by activated
carbon using a process known as adsorption which causes the waste particles
to become linked to the surface of the carbon. When the carbon surfaces
can hold no more they must be replaced.
Zeolite can also be used to remove ammonia and nitrite from the water.
Zeolite is "rechargeable" as it can be cleaned by soaking
in salt water for 24 hours.
If a large biological filter is present then chemical filtration is
not normally required, but is a good alternative to use use while the
biological colony is maturing.
Sand filters
Some Fish owners use a sand filter as a final stage to 'polish' the
water. Water passes through the filter, under high pressure, and comes
out very clear. Desirable bacterial activity also takes place in the
sand filter. However, sand filters are expensive to operate and clog
too easily to be practical for fish or fish ponds.
Bead filters are an excellent alternative to sand filters. They
are similar in function, but very different in terms of the interior
plumbing and media. Instead of sand, bead filters are filled with
thousands of small plastic round beads. The function of these
beads are twofold. One function is to help trap particulate matter
in the water, and prevent it from passing through the filter, while
still allowing the water to pass through. The second function is
to provide a large surface area for the beneficial bacteria to grow on,
this bacteria removes ammonia and nitrite (fish waste) from the water.
