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This is a question to the all the chemists out there...

I have just read about the Ammonia Alert product on the Seachem website. It says there that "If your pH is acidic (below 7.0), it is chemically impossible for ammonia (harmful gas) to exist."

So, let's say I my tank has 7 pH. If I have an ammonia spike in my tank, will lowering the pH to 6.8 will turn my ammonia into ammonium and will then make it safe for the fish?

Short answer: No.

Ammonium is still toxic, just not as toxic as Ammonia. Also, even in acidic pH water, not all of the ammonia is oxidized.

Basically in an acidic solvent (such as acidic tank water) the ammonia is partially oxidized from NH3 to the less toxic form NH4+.

Here's the (unbalanced because I'm lazy) reaction:
NH3 + H3O+ ---> NH4OH + H2O

The extent to which this reaction occurs depends mainly on the pH and temperature of your water. Here's a chart:




Anyway, as you can see the ammonia (NH3) isn't entirely eliminated, it's just not as high in concentration. Even very small amounts of ammonia can be very bad for your fish, especially if you have low dissolved O2.

Also, ammonium itself is toxic to fish, so its presence in the aquarium should not be taken lightly either.

Another interesting point is that NITRITE toxicity actually increases at a lower pH, because the concentration of nitrous acid (highly toxic) is higher.

Bottom Line: High pH or low pH, ammonia is still bad news.


Last edited by tryst at 11-Dec-2004 10:23[/font]

Very true and nice explaination Tryst.

Bottom Line: High pH or low pH, ammonia is still bad news.

But, though toxic all the same, it is less toxic to fish in acidic water than alkaline water.

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