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AMMONIA MACHINES: KOI CAN OVER EAT
David Dec (davedec@decinc.com)
Koi make ammonia from the food they eat. Koi are sometimes referred to as
ammonia machines. The reason for this is because of the quantity of food they eat. This
ammonia is made in several different ways:
Koi respiration introduces ammonia through the gills, urine and feces.
Un-eaten food decomposes into several chemicals including ammonia.
Sediment on the pond bottom, consisting of feces. Plant material from
within the pond as well as windblown leaves and other dead organisms, also generates
ammonia.
We can calculate the ammonia generated by the food my making a few
assumptions:
We feed just the proper amount of food each and every day, which
establishes a “Steady State” condition producing the same amount of ammonia each
and every day. Once we know the weight of wood we feed each day the calculation becomes
easy.
Koi eat a 1% to 2% of their body weight in food each and every day, but
the calculation should be based on the actual weight of food we feed daily.
The protein content of Koi premium pond food is typically 36%, but
sometimes is as high as 40%.
The nitrogen content of protein is typically 16% (the Kjeldahl Analytical
Method is based on this).
So multiplying the weight of the food by the % protein, and then by the %
of nitrogen in the protein, we know the weight of atomic nitrogen going into the water.
If we know the volume and thus the weight of the water, we can then
calculate the ppm of nitrogen.
A few calculation based on these assumptions for a typical Koi pond, show
that this results in the production of 1.6 ppm of atomic nitrogen every day.
a. This creates 1.9 ppm of ammonia
i.(4.3 ppm fir 2% food – 40% protein)
b. 1.9 ppm of ammonia creates up to 5.2 ppm of nitrite
i.(11.6 ppm for 2% food-40% protein)
So each day we generate 1.9 ppm of ammonia, and up to 5.2 ppm of nitrite.
When we measure the amount of ammonia and nitrite actually present, we know the difference
is the amount “digested” by the bacteria daily.
If there are no bacteria to digest the ammonia and nitrite, and there are
no water changes, then the ammonia concentration will increase by 1.9 ppm per day, the
nitrite by up to 5.2 ppm per day.
Under these conditions the Koi will soon die from the toxicity of ammonia
and nitrite. A couple of weeks in water over 20 ppm of ammonia and nitrites and we will
have mostly dead Koi, the ones still alive will have Columnaris and Aeromonas infections,
such as hole in the side disease, fin rot, tail rot, secondary fungal infections, etc. |
