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Re: Boron

Steve Pushak wrote, Jan. 30:

>...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.
Yes. That is the same value I calculated for boron.  I don't change the
water for months, some times years, and I usually make a full change when I
do. I have not been adding any more micronutrients after the initial
addition.  The micronutiient mix I made up was about three times more
concentrated than the original formula described by Johnson, et. al., 1957,
which was mixed up so that you add 1 cc per liter.  I mixed it up three
times more concentrated and add 1/3 cc per liter.

>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?

I don't know how concentrated boron has to get before it starts causing
damage, but I would think it would be somewhere around 50X to 100X the 0.26

>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.

At the low concentrations needed for boron, I don't think it matters
whether the source is borax or boric acid.  I also don't think there would
be any precipitation with other nutrient salts at the low concentration
needed.  After I dose the water with my 1/3 cc per liter of micronutrients,
I usually get enough growth that I want to change the water before I need
to add any more micronutrients.  I think the 0.01 mg/L of boron may be a
bit low.  I have had boron deficiency show up in a tank where I only put
1/6 cc micronutrients per liter, but only after about a year and quite a
bit of growth.  Adding the other half of the micronutrients cured the
deficiency, and I got a lot more growth.

>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....

It might be.  I have seen boron deficiency show up quite soon in a newly
planted aquarium with topsoil and the tapwater available at the college
where I teach.  Obviously, where wasn't very much in the topsoil or in the
water.  I have also seen it show up as quickly when I was at the University
of Wisconsin and was using Lake Mendota water.

Paul Krombholz, in soggy central Mississippi with more heavy rains predicted