The
Basics of Koi Pond Filtration (Page 3 of 3)
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Biological filtration,
as the name implies, employs natural biological processes to convert
the harmful wastes excreted by the koi and those produced by
decaying plant matter in the pond into less invasive compounds.
Koi excrete ammonia, which is deadly to koi in large doses.
Certain anaerobic (non-oxygen-breathing) bacteria convert ammonia
into nitrites, which are, unfortunately, also poisonous to koi.
The good thing is, there are 'good' aerobic (oxygen-breathing)
bacteria that convert nitrites into nitrates, which are no longer
deadly to koi. These 'good' bacteria are also known as
nitrifying bacteria. Nitrifying bacteria occur freely in
nature, and will populate your pond in time.
Biological filters usually use
bio-balls, sintered glass, porous rocks, ceramic rings, or synthetic
high-surface area particles as filter media. Biological filter
media are designed to have as much surface area as possible for a
given volume, in order to maximize the good bacteria population
within the filters. Since good bacteria are aerobic, special
biological filters known as dry or trickle filters are becoming
popular among koi enthusiasts. A dry or trickle filter
just lets the water 'trickle' down through the filter media in
droplets before returning to the pond. Trickle filters don't
fill up with water, allowing the media to get highly oxygenated than
water-filled biological filter chambers. This gives the
aerobic bacteria access to more oxygen.
Figure 4. Examples of various commercially
available filter media
Aside
from the filters themselves, another equally important feature of a
pond's filtration system is the bottom drain. As its name
implies, a bottom drain is a drain at the bottom of the pond where
dirty water is sucked by the pump for transport to the filter
chambers. The bottom drain is normally placed at the center of
the pond, and should be the lowest point on the pond bottom.
Thus, the entire pond bottom surface must slope towards the bottom
drain. A pond with no bottom drain will need frequent cleaning
of its floor. Due to the importance of this feature, there are now
many off-the-shelf bottom drains available in the market.
Figure 5. Examples of bottom drains in the market
These are the basic filtration
requirements of a koi pond. A hobbyist can construct his or
her own filters, or can simply buy off-the-shelf ones.
Sophisticated, easy-to-maintain filters are already widely available
but be ready to spend some big bucks if you opt to go for these.
By the way, ultraviolet lamp
systems for killing algae may also be considered if green water is a
persistent problem for you. In fact, many koi experts consider
the uv sterilizer as a 'must-have' item for successful koi keeping. These are usually placed before
the mechanical filters since uv light makes dead algae clump
together. I've had success designing filters that don't need uv
light to keep the water clear though, so you may want to go for this
as well. Lastly, surface skimmers for removing wastes on the
surface of the pond will also be required by your pond if you do see
this problem during hot summer days.
Pond water quality is the key
to enjoying your pond, so it is better to have a smaller pond with
superb filtration capability than to have a large pond with
undersized filters.
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See also:
Trickle Filters
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