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Re: SAEs weak
At 03:48 PM 8/29/98 -0400, Dave Gomberg wrote:
>I checked the pH and it had dropped from its normal 6.1-6.3
>to 5.4 or so. I started adding NaHCO3 slowly, and brought the pH back up
>to its usual range over the course of six hours.
>
>I checked nitrate (15-20ppm) and Fe (none, I believe the plants have soaked
>it all up).
>I have been adding small amounts of NPK (the plants stopped pearling almost
>entirely and were yellowing, the NPK restored the pearling and
>dramatically decreased the yellowing). Small amounts means a total of 2g
>of (NH4)2SO4 and an equal amount of KHPO4 into 200L over the course of a
>week (a few mg at a time).
I already advised Dave about the dangers of adding an Ammonium compound.
Now I want to share my new comments with the readers of this list.
Adding ammonium compounds can be trouble and my guess is that toxic ammonia
is what affected the SAEs. My guess is that the small additions were
cumulating.
Several years ago I experimented with addition of NH4 compounds and
similarly learned the hard way that adding ammonium is not a good idea. I
killed some livebearers. Although plants prefer ammonium to nitrates as the
preferred source of nitrogen, ammonia or even ammonium in small quantities
can be toxic to fishes. See
http://www.actwin.com/fish/aquatic-plants/month.9603/msg00124.html
The full paper is somewhere on THEKRIB.
>Small amounts means a total of 2g
>of (NH4)2SO4 and an equal amount of KHPO4 into 200L over the course of a
>week (a few mg at a time).
Two grams is not a small amount. Two g of (NH4)2SO4 per 50 gallons will
give an immediate concentration of 1.3ppm of ammonium. Although ammonium is
in equilibrium with ammonia and most of the material will be the relatively
safe NH4 at low pH doesn't mean that it is totally safe. At pH 6.5, .20 %
is still in the form of NH3 (i.e. 0.0026 ppm). From the table provided in
the link above, this amount should be relatively safe. However, if the NH3
lingers for days, this small amount can be bad news . Moreover, the total
of NH4 and NH3 is also a problem, especially if it lingers. The lethal
amount for 4-day concentration is around 0.7 ppm.
Increasing the pH may have made matters worse. This made any residual
ammonium much more toxic, by converting a higher percentage to toxic
ammonia. [This is the same problem that kills fish during acclimation of
tank water into their shipping bag.]
Normally, I would not expect any ammonia after 4 days in a thriving plant
tank. Perhaps the addition of measured nitrate concentration of 15-20ppm is
preventing the plants to remove all ammonia (the plants preferentially take
ammonia, but this may not mean they use all the ammonia before they tank
any nitrates. This amount of nitrates suggests that the plants may already
have an abundant amount in their leaves. So, unless there is alot of
plants and they are growing fast, 1.3ppm of ammonia might be a lot to remove.
>Any idea what I might have done to my SAEs????
Taken them out before the experiment.
--Neil Frank