Altum wrote:

Derek Broughton wrote:
Altum wrote:

Yes, but it's _still_ much less toxic than ammonia.
Put it in alkaline water (as in most ponds) and it promptly loses a
proton and becomes ammonia.

"most ponds"? I think you'd be hard pressed to prove it. I'm not
convinced your chemistry is right, either - mine's way in the past, but
it doesn't seem valid to me.

What part of "pKa of ammonium = 9.2" is unclear? You can verify that
number anywhere. If you have forgotten what a pKa is, you may want to
go back to a chemistry text and review the Henderson-Hasselbach

That would be Henderson-Hasselbalch...

equations and buffering chemistry. Knowing about the pH-dependent
equilibrium between less NH4+ and NH3 is fairly fundamental to aquarium
and pond chemistry.

For those who don't know what Altum meant, there should be equal amounts of
Ammonia & Ammonium in a pond with a pH of 9.2. That's _really_ high for a
garden pond and the first thing I'd want to do is get it down. Since
getting a pond down to about 8.4 is really pretty simple, and the ratio of
ammonium:ammonia is about 10:1 at that pH, I'd suggest it's not as serious
a situation as he says.

See http://www.reefkeeping.com/issues/20...hf/index.php#2 for a nice
graph (slightly different from our situation because of salt water, but
close enough).

Now, if we're going to revise the argument and point out that it doesn't
matter that _all_ of the ammonium won't instantly become ammonia, but that
any amount of ammonia is a Bad Thing (TM), I'd pretty much have to agree
and point out that that's one reason why planting in clay soils is usually
recommended. If you're going to fertilize lilies, you should plant in a
clay soil, and use solid fertilizers in the soil. Not much will migrate
out of the clay before being used by the plant.

However, it's all complicated by the fact that bacteria are constantly
converting ammonia to nitrite & nitrate, and _any_ pond can remove some
amount of ammonia from the water - which is why so many people manage to
continually top up their ponds with tap water without killing the fish.
--
derek
- Unless otherwise noted, I speak for myself, not rec.ponds.moderated
moderators.