Page 72 - Koi Net - On-Line Koi Magazine - Issue 92
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how much Ammonia is excreted based on the body through the rain per year (measured in 1998). In the
weight of also larger Koi per day. Instead, it can be seen Netherlands, according to a research firm V-focus, the
from all this data that it depends in particular on the RIVM (Dutch government research institute) once
food, at least the highest peak excretion and the total estimated that this would be 25-60kg per hectare.
maximum quantity per day. V-focus raised questions to this in 2014 and went on to
perform some measurements and calculations itself.
Is this the whole story? Well no, because there may Their conclusion was that in the Netherlands it would be
theoretically be other sources of Ammonia (TAN) that on average just over 10kg/hectare which is pretty high in
come into the water; other food sources for your Koi; comparison to other countries. What does this mean for
and how do we get rid of that Ammonia? That’s all our ponds? One hectare is 100 by 100 metres, so
covered in the next few articles. More in depth 10,000 square metres. So per square metre, per year,
knowledge, and the completion of the Ammonia chapter.
1 gram of nitrogen falls into your pond. Let’s take a large
The conclusions of the first articles were predominantly pond of 10 × 10 metres (1.5m deep gives 150m³),
based on studies with fish in a clean container of water, 100 square metres gets 100 grams of nitrogen per year.
in a laboratory environment. It makes sense then that We divide this by 365 days. That is 0.27 grams of
one can measure what carp eat and excrete precisely. nitrogen per day in a pond of 100 square metres. I think
These tanks are also called a Recirculating Aquaculture that more than 100 grams a day will be fed there in the
System (RAS). In other words, tanks with fish where the summer. In that 100 grams feed there is already
waste is kept under control by filtering and recirculating 7.2 grams of nitrogen. Someone with a pond of 150m³
the water. Sounds familiar? Sounds almost like the most probably gives closer to or over 500 grams of food
average Koi pond to me. The difference is that our per day so that Ammonia addition through rainfall is
ponds are outside and stay like that for years. Rainwater becoming quite negligible.
falls in with Ammonia in it, which is now a hot topic on
In the average Dutch tap water the concentration is
TV. What would be the influence of that? And would an
below 0.02mg/l which is also below 0.02 grams per m³.
extra nitrogen cycle arise, like in mudponds, where
In the example of 150m³, a whopping 60m³ of water at a
nitrate is absorbed by algae (phytoplankton), which is
40% water change is added at once, which is 1.2 grams
then eaten by zooplankton (lobster-likes), which can be
maximum, per week. At the same time, you also let
eaten again by Koi? If extra Ammonia enters the pond
60m³ pond water run away in which the average pond
via the rain or tap water, this system can theoretically
contains much more Ammonia, nitrite and/or nitrate,
build up to a point where you never have to feed the
and bacteria (contains nitrogen), and floating algae (also
Koi again.
contains nitrogen) as in tap water. So by changing
Will there be extra Ammonia in the ponds that do not water, you will by definition remove nitrogen compounds
come from the food? Let’s take a look at the possible from your pond. Conclusion: the main nitrogen source in
sources, being tap water and rainwater. our ponds is the food.
There is a Nitrogen problem in places in the Is food the only food source for Koi in our Koi ponds?
Netherlands. Where there is more additional Ammonia Or does, perhaps, a second food cycle play a role
created by the rainwater than the ecosystem can handle simultaneously in the pond? I go to the next article, the
in places, and there will only be more incidents of role of carp in aquaculture production systems from
acidified soil and trees that die, according to the 2015. In the breeding ponds (mudponds) one tries to
literature. Ammonia from rain also falls into our ponds, recreate a mini ecosystem as quickly as possible as it
but how much is that? According to the National occurs in the natural environment of a carp. That is,
Atmospheric Deposition Program (NADP) in the USA, there are a lot of nutrients in the water (manure is
the worst hit states get 7kg of nitrogen per hectare frequently thrown into a pond), from which bacteria are
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