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[APD] Re: Ammona and Soil Substrates

Jim said:
> Back to your problem: have you measured the pH of your tap water? It may
> much more acidic than your tank water. Maybe it has large amounts of CO2
> added to prevent scale buildup in the Laguna Madre causeway?
Jim, thanks for the reply.  I have more information.

I'm not familiar with the acidification but I know from D. Walstad's book
that the total amount of ammonium and ammonia in a tank are in equilibrium.
At a PH of 7 and at a PH of 8, the total amounts of these two compounds are
the same, but the amount of ammonia is 10 times greater at a PH of 8 than at

My tap water is about PH 7.9, and I keep the tank at about PH 7.1-7.0 with
CO2 injection (KH = 6.5).  So if I do a 50% water change the PH may go to
7.5.  So if ammonia is in the tank before I do a water change and the PH
goes from 7.0 to 7.5, even though there is no ammonia in the tap water,
there is a good chance that the ammonia in the tank will increase due to the
PH change.  This is because the change in PH shifts the ammonium/ammonia
equilibrium towards the ammonia side of the equation.

However, in the case of this tank, the ammonia in the water column was zero
before the water change.  For the ammonia to increase after the water change
I feel that  the only place it could have come from was from the soil
substrate.  Perhaps the change in PH affected the soil rather than the
hydrostatic pressure as I had originally suggested.

As a control, I did the same water change on another tank that has a
gravel/laterite substrate and the ammonia was zero after the water change.
The fish were energized after the water change instead of distressed (dead).
I don't think the city would add co2 directly to the tap water, but if they
did I would think the PH would be much lower for my tap water.


Steve Pituch

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