# How to calculate NH3 in your pond

#### MitchM

I came across a table and a calculator that a person can use in order to calculate the free ammonia (NH3) level in their pond (or aquarium) when they get a positive reading on their ammonia test kit.
The maximum recommended NH3 level for koi is .02 milligrams/liter, long term.

You need 3 values to determine if your fish are at risk - Temperature (celsius), PH, and the ammonia reading from your test method.

Here is a calculator where you plug in your numbers to determine the actual NH3 level:
http://home.eng.iastate.edu/~jea/w3-research/free-ammonia/nh3.html

Here is a chart that displays the maximum allowable TAN (Total Ammonia Nitrogen) reading, in parts per million (ppm) from your test method.
The chart below came from this website: http://mankysanke.co.uk/html/ammonia.html

Parts per million (ppm) = milligrams per liter (mg/L) Last edited:
• Meyer Jordan and morewater

#### Meyer Jordan

I came across a table and a calculator that a person can use in order to calculate the free ammonia (NH3) level in their pond (or aquarium) when they get a positive reading on their ammonia test kit.
The maximum recommended NH3 level for koi is .02 milligrams/liter, long term.

You need 3 values to determine if your fish are at risk - Temperature (celsius), PH, and the ammonia reading from your test method.

Here is a calculator where you plug in your numbers to determine the actual NH3 level:
http://home.eng.iastate.edu/~jea/w3-research/free-ammonia/nh3.html

Here is a chart that displays the maximum allowable TAN (Total Ammonia Nitrogen) reading, in parts per million (ppm) from your test method.
The chart below came from this website: http://mankysanke.co.uk/html/ammonia.html

Parts per million (ppm) = milligrams per liter (mg/L)

View attachment 96608

Did a quick comparison of the Iowa State calculator linked above to the calculator that has been used for many years that was originally from a New York Koi club.
http://www.koiphen.com/forums/koicalcs.php?do=calcnh3c

The results are quite different. So which one is right?

#### MitchM

I just plugged .25 tan, 10c and 8.2 PH. I got the same results in both - 0.007 nh3
Which values did you use?

#### Meyer Jordan

I just plugged .25 tan, 10c and 8.2 PH. I got the same results in both - 0.007 nh3
Which values did you use?

OK. The Koiphen calculator is rounding-ff to the higher 3 decimal value. Maybe not so different after all.

#### MitchM

I tried to find the algorithm from the Iowa State calculator so I could double check, but the webpage for the formula is no longer available.

#### Meyer Jordan

I tried to find the algorithm from the Iowa State calculator so I could double check, but the webpage for the formula is no longer available.

Is this what you are looking for-

EQUATION 1.
pKa = 0.0901821 + 2729.92 / T
Where,
T = Temperature in K; Absolute zero = - 273.15 oC
T (in K) = T (in oC) + 273.15
EQUATION 2.
f = 1 / [10 (pKa - pH) + 1]
Where,
f = fraction of total ammonia that is un-ionized
pKa = dissociation constant from equation 1

• MitchM

#### MitchM

Ha, maybe. I'm still kicking myself for not saving a hard copy of the original pond heat loss calculator I had.
I would like to make up an Excel worksheet so I don't lose some of these calculators.
The Iowa calculator is from 1998 and the Koiphen original source (New York Koi Club) for their ammonia calculator is no longer around.
Thanks.