# [APD] Ammonia

```I believe David Marshburn wrote this email section below:
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Stuart Halliday wrote:
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So in theory by adding ammonia drops to my tank, the plants would only take up the ammonium part and leave the free ammonia behind?
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sort of. free ammonia and ammonium are in some equilibrium, depending on pH. as plants pull out the ammonium, some of the free ammonia will shift to ammonium ion (and i suspect that the pH will be affected).
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I thought that.

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here's the first article on ammonia/ammonium equilibrium that popped up on google, and it seems pretty good, if maybe a bit mathy.
```http://equilibriums.beggiatoa.com/ammonia.htm
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notice that, in order to go from ammonia to ammonium, the ammonia had to snag an H+ from the water, leaving a free OH- hanging around (this is why ammonia solution is considered basic).
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So the ph will rise and move towards the alkaline, buffering permitting?

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also, the relative fraction of ammonia and ammonium is affected by pH. at pH of 9.24, it's a 50/50 split. at higher pH, there will be more ammonia; for "most" (?) planted tanks, the pH is closer to neutral, so most of the ammonia is in the form of ammonium.
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Yes, I've noticed that.
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A friend of mine was sweating buckets over a new tank with a pH of 7.4 @ 25C and a TA of 0.25. I said don't worry too much about it. That's 0.004ppm of NH3. Virtually harmless to his adult fish. I said, just use Prime or do a 25% WC if he was worried and eventually it will go away. It did.
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this calculator will tell you how much ammonia vs. ammonium you have, based on total nitrogen concentration, pH and temperature
```http://cobweb.ecn.purdue.edu/~piwc/w3-research/free-ammonia/nh3.html
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Ah good old Professor Alleman.
We can find his original equations here:
http://web.archive.org/web/20050319163127/http://ce.ecn.purdue.edu/~piwc/w3-research/free-ammonia/derivation.html
or via my Ammonia page.
http://theaquariumwiki.com/Ammonia

I quite like this online chart below as it shows the toxicity levels:
http://www.cnykoi.com/calculators/calcnh3c.asp

A few months ago, I managed to find where these 'toxicity levels' came from
if anyone is interested:

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US Environmental Protection Agency. Ambient Water Quality Criteria for Ammonia, (EPA 440/5-85-001). January 1984-2004
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http://www.epa.gov/ost/pc/ambientwqc/ammonia1984.pdf
http://www.epa.gov/waterscience/criteria/ammonia/99update.pdf
http://www.epa.gov/ost/standards/ammonia/99update.pdf

--
Stuart Halliday
http://mytriops.com/
200 Million years in the making...
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