[APD] RE: CO2 and ammonium chloride

["Thomas Barr" <tcbiii at earthlink_net>]

"I do add KNO3 and it seems to be working well.  I dilute it to about 2 
mg/drop and dose judiciously to avoid algea growth.  Plants prefer amonia
to nitrate 
because it takes them less effort to absorb it or use it."

Algae prefers NH4 far more than the plants do in terms of growth and is
much less influenced by NO3. I've kept higher NO3(10-20+ppm) and not found
increases in algae even without any algae eaters at all.

 "You asked, "What does amonium chloride have to do with CO2?"  Well, I
suppose 
that with enough light and CO2 a plant would better be able to utilize the 
amonium in amonium chloride."

You will not get any more growth out of a plant beyond about 30ppm of CO2
no matter what the light level is. The plants tend to max out at about 600
micromole photons/m^2/sec, or about 30% full sun in the tropics. We do not
need more light or CO2 than this because the plants simply can not use it.
That is their max growth rate for both light and CO2. These parameters are
based on fast growing submersed stem plants. Slower growers will likely
have less requirements/demands.
Algae can use more light and seldom are CO2 limited(they can use HCO3 as a
generalization while only a few plants can). Both plants and algae prefer
CO2.   

" However, there might be too much chloride in it.  
For the benefit of those of you that don't know these things, our fish 
conveniently provide the tank with amonia.  It's just sometimes not enough
to 
adequately fertilize the plants which is why we dose potassium nitrate
KNO3.  We 
don't add amonium because it can convert to amonia which is toxic to fish.
Sincerely, George Mangen"

The issue is the shear volume of Nitrogen required by plants can never by
supplied by NH4 without causing an algae bloom.
This level needed to cause an algae bloom is far below the level needed to
kill fish. Algae is therefore much more the issue than killing the fish in
a planted tank.
Even small trace amounts are enough to induce a bloom and often it takes
just a few hours or perhaps a day or two for this to occur.
Don't believe it? Try adding NH4 and no NO3 to see or add more and more
fish while keeping the CO2/light/PO4/K/Traces etc constant.
 
It's not the chloride that causes any issues for you, it's the NH4. You can
use ammonium sulfate if you wish to try and isolate the Cl- issue.
This is what I used in the past. There are various salts and compunds you
can use to isolate the nutrient of interest. 

I've done the NH4 vs the NO3 and I've found better growth without fish and
dosing NO3 as the only source of Nitrogen.
I did not expect this.  
Some plants might vary. Some plants might grow better and prefer NO3 at
high elevated CO2 levels while at low or limiting levels the plants prefer
NH4. 

Bowes, Ozimek have done studies to show that Hydrilla and Egeria grows
faster with NH4 vs NO3. But.......you cannot assume that the plant will
behave the same when the CO2 level is 5x higher because these researchers
never tried adding these high levels and NH4, but our tanks have high
levels of CO2....

You can make this arguement much better if you are talking about non CO2
plant tanks. But even there, many assumptions creep in.

If you limit the growth rate with light or with CO2, then also this
decreases the NH4 and NO3 uptake as well...........
Basically you are left to try it yourself and see if the results are true.
If you approach it carefully, you can find some trends. 

The plants clearly did better and had less algae growth with the NO3 test
tank that had no fish or critters except for the errant snail or micro
invertebrate. 
All dosing was from KNO3/K2SO4 or Ammounium sulfate+ K2SO4.  
 
Regards, 
Tom Barr



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