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Re: need help identifying deficiency

>> On Tue, 6 Apr 1999, Aquatic Plants Digest wrote:

> On Tue, 6 Apr 1999, Roger Miller wrote:

>> (ripped from water company web site)
>> Hardness, Total mg/L 7.71
>> Hardness as CaCO3 mg/L  5.34
>> Sodium mg/L 0.003> Calcium mg/L 0.002
>> Magnesium mg/L 0.575
>> Due to the utter lack of Calcium and Magnesium in my
>>water, I supplement it with CaCO3 and MgSO4 to raise it
>>to 80 mg/L of CaCO3 and 20 mg/L of MgSO4.
Is it possible to furnish the URL of the water company report so
we may view the particulars directly?

If the Ca and Mg have been supplemented at those levels for any length
of time,  I think the likelihood of a deficiency or imbalance for those
is quite low.

> 1.  A few months ago I asked the list how low the hardness could
> be without encountering calcium and magnesium deficiencies.  I didn't
> get very many direct answers at that time.  Anyone that's got some
> input here might like to speak up now.  I suspect that others on this list
> are growing plants with less calcium and magnesium than your supplying.
My tap contains soft water:  Ca=18mg/L,  Mg=2 mg/L.  This is not
enough Mg for my plants.  It gets supplemented.
> 2.  Like I said in my first note,  I think the Dupla fertilizers carry
> what they think is sufficient potassium.  I don't do Dupla myself, so
> someone who has experience mixing KNO3 into a full Dupla regime
> might want to pipe up.
Dupla contains about 7 mg/L of K.  Under normal circumstance ( see
below ), this should be fine.  You won't hurt yourself by dosing K to a
higher level.   You could push it to equal your Mg level safely.

>Certainly you wouldn't need to add the KNO3
> for the nitrate. I guess I am looking for some obvious error before I
> start adding Nitrates. Is there a form of Potassium other than KNO3
> that I am overlooking? I'm with you on that; it's best to know the
> problem before you start adding things to solve it.  If you want to dose
> potassium you can also do it with potassium chloride or potassium sulfate.
> There are a couple other things you might think about. Problems with K,
> Ca and/or Mg can be caused by an imbalance in any of Na, K, Ca and
> Mg (this tidbit comes from a review of nutritional needs in hydroponics -
> normal agricultural sources seem to indicate less sensitivity to the
> problem).
I think the observation - frequently sighted - is valid and must include
consideration of the type of nutrient.  Cations tend to compete with other
cations,  anions w/ other anions.  I also believe that the competition for
uptake in aquaria must consider that we have both foliar and root
mechanisms for nutrient uptake - hydroponics and soil farming tend to
rely more root mechanisms.  Thus in aquaria I don't think two cations
would severly compete w/ eachother for uptake if one is abundant in the
water column, the other in a nutrient rich soil.  Thus imbalances and there
consequent  _plant_  deficencies must at a minium consider:

    (1) type of ion
    (2) ratio of that ion to similar ions
    (3) the type of substrate

In either case,  I think that any imbalance must be fairly severe - perhaps
from a dosing mistake ( what's the difference between a gram and a milligram
anyway !)  or a natural imbalance.  Actually,  water authorities tamper
with pH and lime to precipitate hardness,  creating potential for high Ca,
Mg.  The bottom line is to know thy water.

> Since your water apparently is very clean - rather like RO
> water - you might try using one of the mixes used to reconstitute RO
> water instead of dosing individual chemicals.  The prepared mixes should
> give a balanced composition.
This is good.  Question for Kent R/O folks:  Is dosing at their recommended
level for "soft" water sufficient or is there still need for addional

Christopher Coleman
christopher.coleman at worldnet_att.net