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boron concentration

I'm working on a nutrient dosing formula which does not contain iron to
be used with peat+soil substrates so we won't be adding the traditional
trace nutrient mixes. The element I'm worried about is boron. The
concentration in our Vancouver water is not detectable which means its
less than 0.04 mg/L What are typical values for boron concentration in
places which don't have tap water almost like rain water?

I've been searching through the archives looking for information on
boron which can be gotten from boric acid (H3BO3) or borax
(Na2B4O7-10H2O). I also was curious about borosilicate which might be
less soluble and suitable as a substrate additive. My dictionary says it
occurs naturally. What's the solubility of borosilicate?

Paul has said in the past that boron deficiencies can develop in soil
substrates where the water is changed infrequently. He described a
micronutrient mix he uses and he describes a dosage based on water
volume. What you didn't say, Paul, was if this is based on irregular
additions or with water changes. You do say you don't change the water
in most of your tanks. If I've done the rough calculations properly, you
dose 4cc/gal of a solution of 1546 mg/L. That's a dilution of about
1000:1 so I make your dosage out to about 1.5 mg/L of boric acid. The
molecular ratio of boron in boric acid is 10.8 / (10.8 + 3 + 3 x 16) =
17.5% so your target works out to be about 0.26 mg/L of boron.

What is the range of concentrations that would be acceptable for boron
in aquarium water? What are the consequences of boron toxicity in plants
and fish? I read in the APD that some vermiculites might contain
excessive amounts of boron or fluorine; comments? Is the same true for
kitty litter? Since kitty litter is not designed as a growing medium, it
could be made from layer clays not suitable for agricultural use. I'm
not saying it is but I'm sure there's a pretty wide range of substances
that could be used to make KL.

Which would be better to use in the aquarium if it were being added on a
dosage basis with water changes, a solution of boric acid or borax? Will
borax or boric acid react with a solution of magnesium sulphate,
potassium sulphate and potassium nitrate? I think I read that boric acid
reacts with carbonates. I suppose I should use a ratio of boron to
potassium as found in plant tissue to determine the appropriate dosage
in water. My target is 10 ppm of K in the exchanged water. Am I correct
in thinking that the boron is going to stay in solution and not
precipitate? Using a couple of references in the archive I deduced that
the ratio of K to B in plant tissue is about 1000:1. With this ratio, I
could target as low as 0.01 mg/L boron.

Maybe there is so much boron in 90% of tap water samples, that I
shouldn't worry about boron supplementation where there are regular
exchanges of aquarium water....

Steve  fretting about boron in Vancouver
Aquatic Gardeners Association