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Re: use of ammonium sulfate - be careful



---------- Forwarded message ----------
Date: Wed, 15 Jan 1997 06:09:27 -0500
To: Aquatic-Plants at actwin_com
From: Neil Frank <nfrank at mindspring_com>
Subject: Re: use of Ammonium Sulfate - be careful

-------------------------
>
>From: "David W. Webb" <dwebb at ti_com>
>Date: Tue, 14 Jan 1997 15:45:16 -0600
>Subject: re: anubias turning yellow

>The anubias melt and phosphate release turned my tank into a cyanobacteria
>heaven, so I decided to pull a PMDD-ish trick and start adding more
>nitrogen to the tank to provide a known limitation to the plants.  At the
>same time, my snails had paper-thin shells and weren't able to reproduce,
>so I decided to help them out as well.
>
>I went to a feed and seed store and picked up a 5 lb. bag of ammonium
>sulphate, plus a half pound of crushed limestone.  I've been adding about
>1/8 teaspoon of ammonium sulphate to my half-full 55g tank daily, and about
>1/4 teaspoon of powdered limestone on a weekly basis.

Please be careful when using ammonium as a nitrogen source. Ionic ammonia
(NH3) is in equilibrium with ammonia (NH4) and is very toxic to fish. This
relationship is pH and temperature dependent. More so on pH than temp.
Some fish are also more sensitive than others. There is both a short term
and a longer term effect at much lower concentrations. Hopefully, in a plant
tank the NH3 gets sucked up fairly quickly, but I have never figured out how
quickly this happens. Probably a function of the number of plants and growth
rates.

You may be OK in your tank, but the novice should be careful. Because the %
NH3 reduces by 2/3 for every 0.5 decrease in pH, the NH3 concentration may
be low enough at your pH and plant conditions. For example the NH3 at 77
degrees is 0.18% of the total ammonium. However it doesn't take much for the
concentrations   to be lethal. 

Based on published values:

pH      duration      Lethal Ammonia Conc.(mg/l)
                         total   NH3 portion
---------------------------------------------
6.5     1-hr             14.3    0.036
        4-day             0.73   0.002


7.0     1-hr             11.6    0.093
        4-day             0.74   0.006


Note: Sub-lethal may not be that good either! I looked into this subject a
few years ago when I decided to experiment with ammonium chloride to perk up
my plants. After half the guppies in the tank died, I started to wonder!  I
now use either VERY small quanitities of ammonium or use nitrate compounds.
More info is in my article on the Krib (also can be found in the back issues
of FAMA and TAG)


Neil Frank      TAG editor         Raleigh, NC