The Basic Nitrogen Cycle
The waste products from the fish
in their initial form are mainly expressed as ammonia which is
poisonous in even small quantities and especially so under certain water
conditions - high pH - which will be discussed later.
In a mature pond a class of bacteria in the biofilter removes the ammonia almost as soon as it is formed.
The ammonia is converted into other nitrogen chemicals called nitrites.
Another type of bacteria also
present in the biofilter then converts the nitrite chemicals into
nitrate chemicals. These chemicals are less polluting and toxic than
either ammonia or nitrites - both of which are poisonous.
These chemical processes are
occurring all the time and will not stop unless the biofilter system
stops working or the source of nitrogen is removed - ie no fish in the
pond, or the water becomes devoid of oxygen.
The health of the pond is
determined by this relentless ongoing conversion of ammonia to nitrates.
It must NOT stop for the sake of your fish.
If pond water is changed
frequently then to some extent the poison levels are "controlled." The
more fish in the pond then the more the waste products to get rid of.
Koi produce 3 times more waste than goldfish of the same size - because
they eat 3 times more.
The fish food used
has a significant impact upon the amount of waste produced. Do not use
foods with high ash contents - this indicates low quality raw materials
have been used in the food manufacture which result in water pollution
levels being higher than necessary.
In a natural stream or lake fish
concentrations are generally low. Waste products are converted to
relatively harmless nitrates by naturally occurring bacteria. Rocks,
submerged trees, plant roots, etc all help to purify the waste products
from the fish by providing holding points for the bacteria to live on.
The more bacteria there are the better the purification.
The bacteria need oxygen to
survive and they get this from the water - oxygen is absorbed by the
water due to the action of waves, waterfalls and wind.
In a garden pond a bio-filter is installed to make up for the
unnatural conditions prevailing. A biofilter is designed to allow large
concentrations of bacteria to operate effectively in a small volume
within a garden pond environment.
Correctly specified and
installed biofilters create healthy environments in which fish can live
for many years and grow to their full potential.
In small ponds the filter can be
installed directly in the pond. For larger ponds the filter needs to be
installed outside of the pond. The pump connected to a biofilter must
run 24 hours every day otherwise the bacteria will die from lack of
oxygen contained in the circulating water. It is a good idea to have a
waterfall and a fountain to increase the oxygen content of the water.
It is difficult to add too much oxygen to a pond.
Once the bacteria have died it will take approximately 5 more weeks for them to regain close to their previous levels.
What is happening inside a biological pond filter?
The primary job of a biofilter
is to convert ammonia (or ammonium) to nitrites and then to nitrates
using specific bacteria types. In practical terms this requires that
ammonia, which is dissolved in the circulating water, must make contact
with bacteria at an interface and in conjunction with oxygen in such a
way that a chemical reaction can take place.
Once the chemical reaction has
taken place then the product of the reaction which is nitrite or nitrate
must be able to be transferred back into the body of the circulating
water and removed from the immediate presence of the bacteria to make
way for the next bit of ammonia.
Therefore a well-designed biological filter MUST have...
- A large surface area on which bacteria can grow and to which a maximum amount of pond water can be exposed
- Biofilters work best at higher flow rates/lower residence times - ie turbulent flows are best.
- The presence of large amounts
of oxygen at the interface also creates the concentration differences
required for good mass transfer. This is why top class koi keepers have
vortex filters and blow massive amounts of air around the biomedia that
is generally Japanese matting.
- Biofilters work best at higher temperatures.
Sand Filters For Use In Pools Are Bad For Garden Ponds
Sand filter are used for the mechanical filtration of solids, not to be confused
with fluidized sand filters, which are used for biological filtration.
Although the size of particle that the sand filters remove is dependant
on factors such as the size of the sand particles, the depth of the bed
of sand and the flow rate through the bed, sand filters are usually
regarded to filter water to a nominal 10 microns.
... The first is a simple box
structure that operates with a low pressure across the filter. The water
flow-rate to cross sectional area ratio of such filters is low, and the
filters tend to rapidly block in the first few centimeters, with the
rest of the filter staying clean.
Such filters are only of use in
applications where the use of pressure filters is impossible or the
water is generally clean and there are only a few particles that need
removing. Such an example may be a ground water supply which is thought
to be contaminated with pathogens through seepage into the spring /
borehole. Large filters of this design are difficult to clean
effectively, usually resulting in the bed being periodically dug out and
replaced by fresh sand.
Pressurized sand filters are in
common use in many aquaculture applications. They consist of an enclosed
vessel that is typically half to two thirds full with sand. Water is
pumped into the top of the filter under a pressure of approximately 1-2
bar and is forced through the sand to a water-collecting device at the
bottom that allows the water through, but not the sand particles.
The flow is then reversed to
back flush the filters. Pressurized sand filters are expensive to use
for high flows due to the cost of pumping the water through them. They
are however used extensively in hatcheries and also some recirculation
systems, where they are either plumbed in for all the water or as a side
stream, where only a percentage of the water flows through.
Their limitations in
recirculation systems is that, in addition to the operational costs,
they use a lot of water for back flushing (a typical sand filter in a
recirculation system will require back flushing 4-6 times a day for 5
minutes each time. The water flow rate whilst back flushing is the same
as the flow rate when filtering).
This is exacerbated by the fact
that sand filters in re-circulated water will also act as biological
filters, and a layer of heterotrophic and nitrification bacteria will
build up on the sand, causing channeling and increase back washing
frequency.
The back wash process is
insufficient to eliminate all the bacteria that soon multiply and block
the filter again. A way round this is to add ozone or other disinfectant
chemicals to the water when back flushing (the advantage of ozone here
is that any residual amounts after back flushing will quickly be
neutralized by the organic compounds in the water). Now that
self-cleaning mechanical screen filters are available with screens of
less than 10 microns, the use of sand filters is becoming less common."
PURE POND BOMB adalah konsentrat PURE POND. PURE POND BOMB sangat ideal untuk digunakan di kolam Koi, kolam hias, atau kolam yang tidak memiliki filtrasi konvensional, untuk mencapai air jernih yang sehat.
PURE POND BOMB adalah konsentrat PURE POND. PURE POND BOMB sangat ideal untuk digunakan di kolam Koi, kolam hias, atau kolam yang tidak memiliki filtrasi konvensional, untuk mencapai air jernih yang sehat.
Ideal for garden ponds up to 10,000 litres
