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Nitrate addition

Susan Romano wrote:

>Interesting observations from Steve regarding calcium deficiencies, Karen
>concerning  potassium nitrate and Eric about CaCO3 and MgCO3. Interesting
>for me because I can't seem to grow java fern at all. I have great success
>with another fern,  Bolbitis heudelotii with only CO2, Flourish fertilizer
>and light. My nitrate level is undetectable with my Tetra nitrate test kit.
>It might appear that  Bolbitis heudelotii(why no common name as she types
>furiously), a rhizome typical plant,  can possibly make due with little
>nitrate as I assume that the other elements are covered in my
>fertilizer(all other plants are doing great). Calcium I add by daily
>scraping a little of a Aquarium Pharmaceuticals vitamin/mineral pyramid
>into the tank. The Bolbitis grows like gangbusters on very little nitrate
>it seems, as it receives no assistance via the substrate. I have even had
>good results from Bolbitis  with no CO2. 

I also keep B. heudelotii and another species of Bolbitis (not heteroclita
- this one is another African, and more similar to heudelotii) in several
tanks, and it grows very well for me. (to the point of being invasive at
times<g>)  I do not happen to have any in this tank that suffered neglect
and in which the Javas melted, so I'm not sure whether the Bolbitis would
have been affected or not.

>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.  

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?

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

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.  Use
very small amounts and don't raise the nitrate level above 5 ppm. (I use
even less)  Watch your plants.  If you have algae problems after this
treatment, you may have guessed wrong, or you may have high PO4 levels in
spite of the low nitrate.  But if the plants are using nitrate well, your
levels will soon back to insignificant if you don't add more.  If the
plants respond positively, you should see increased growth and a slowing of
the loss of older leaves quite quickly. (within a week or so)  

After a while, you'll get a feel for when you need to add nitrate just by
watching your plants.  I tend to err on the cautious side though, and test
to make sure that my observations agree with the test results before adding
more.  It is _much_ easier to increase nitrate levels than it is to solve
algae problems if you add too much!  If you are not running a CO2 injected
high light tank, with low-moderate fish load, the chances are _very_ slim
that your plants are nitrogen limited.

Karen Randall
Aquatic Gardeners Association