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Re: Nitrate addition

>Date: Tue, 08 Dec 1998 09:33:11 -0500
>From: krandall at world_std.com
>Subject: Nitrate addition
>>Also, after reading Karen's post I
>>wondered why she needed to add any nitrate to a neglected tank. In my
>>experience when I neglect the tank,(stuff happens), the nitrate really
>>shoots up. So does the green algae. Please excuse me now while I go change
>>some water.
>While I agree with you that it is _much_ more common for tanks to have to
>much in the way of macronutrients than too little, it is not always the
>case.  Many of us who have high light/strong growth tanks need to
>supplement nitrate from time to time.  

Since my tanks are neglected most of the time <g>, I can really relate to
this thread.  Because I keep a low fish load in almost all of my aquaria,
including those w. added CO2, those tanks always have low nitrates. When I
neglect them, they are likely to miss their biweekly water change. My tap
water contains 2 ppm of Nitrogen. Some of this comes from the ammonium
released from the chloramine. Therefore, my plants get some of their
nitogen supply from the periodic water change.

Usually, this nitrogen plus the amount from fish food, animal waste
products and recyled vegetation is enough to maintain my desired plant
growth. When I am looking to get higher growth, or to respond to N
deficiency expecially in heavy feeders like Echinodorus, I add nitrates. (I
once tried to add ammonium directly, but do not recommend this. Too much
and a toxic situation can occur, even with low pH). The easy to obtain form
of nitrates is Sodium  Nitrate (Nitrate of Soda). Years ago, I bought my 2
pound bag (lifetime supply) for 3 bucks at garden section of the hardware
store. (The quality is more than adequate for aquariums. I have been using
it for almost 10 years).  As many of you have already noted, KNO3 is not
easiest to obtain material... also, it is more expensive than nitrate of
soda. KNO3 is only better if (a) you already have it on hand because it is
part of your normal fertilizing regime (e.g. PMDD) or (b) you use
commercial fertilizer and it DOES NOT contain potassium (K). IMHO, there is
no need to specifically add more K without the complete complement of other
elements that are routinely added with your plant fertilizer. If Karen is
using Tropica Master Grow, the K is provided in proper portion to the trace
elements. Neglecting the weekly fertlizer or bi-weekly water change is MUCH
more likely to cause deficiency with trace elements than K. 

Here is a comparison of the Nitrogen from NaNO3 and KNO3:

Compound		Weight (g) 	   Analyte	    Concentration (ppm)
			per 1/4 tsp.   		    of 1/4 t in 50 gallons
sodium nitrate		1.8       	NO3-		7.0
NaNO3                                N+          1.5
(Nitrate of Soda)

Potassium nitrate 	1.4   	NO3-		4.5
KNO3						N+          1.0
(Salt Peter)	            

>I don't recommend doing this unless you are _SURE_ that the plants really
>_are_ nitrogen deficient.  If you suspect a nitrogen deficiency, this it
>the procedure I would suggest:
>1. Observe the plants.  Are the OLDER leaves deteriorating too quickly?
>Are the OLDER leaves turning yellow, while new growth, although normal in
>color and shape is smaller than previous growth?

Another indicator is duckweed. I seem to always have at least a few
floaters in my tanks and when the duck weed is NOT spreading  or is
chlorotic, I think about N. If I am doing my routine fertilization and
feeding the fish, I am pretty sure I have an N deficiency. In the extreme
example -if the tank is getting fertilizer with K and I am NOT feeding the
fish and the substrate has been undisturbed, then P may also be deficient.
P is also needed for water feeders like ferns and in my described (albeit
unusual) situation, it can also lead to a meltdown.

>2. Make _sure_ there is no measurable nitrate in the tank using a good
>quality _low range_ test kit.

After you test your tank once for nitrates once or twice and find that the
concentration is always less than a few ppm (say 1-5), and you are
periodically removing plants from the tank, then you can be pretty darn
sure that the nitrates are still low. This is a "feel" than you can develop
for your tank.

>Only if both of the above are true should you consider adding
>macronutrients to a tank.  If you are pretty sure you have a macronutrient
>deficiency, the safest way to test your theory is by inserting small pieces
>of a low phosphate slow release terrestrial plant fertilizer around the
>roots of affected plants.  (I have successfully used Jobes Plant Sticks for
>Ferns and Palms) 

>If you want to be more daring, you can add KNO3 directly to the water.  

I guess I am much more daring than Karen.:-) IMHO, it is MUCH safer to add
a 1/8 t of Nitrate of Soda (or KNO3) to 50 gal of water than a small piece
of jobes stick. The former will raise N less than 1ppm and may be less than
a water change. OTOH, the stick can release its water soluble phosphates
into the water and this can feed algae more than a small amount of nitrogen
alone. With a little practice, you will see that in a tank without a lot of
visible algae, even more N can be added without causing algae because the
plants will quickly suck it up. In fact, adding the N will cause the algae
to recede (one of the principles of PMDD). One must be careful to not over
do it or a deficiency can occur in another element... or your plants will
start growing faster than you wish:-) So, balance is needed and the N must
not be added in proportions that for example exceed the ratios in PMDD.
When I want that extra oomph from my plant growth, I add a small amount of
Nitrates with my addition of commercial fertilizer. But I need to be
prepared for the extra work during the monthly trimming.:-)