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Re: Substrate idea and water quality questions

Bob Dixon wrote:
> I am thinking about trying a new substrate clay in lieu of laterite.  It is 
> pyrophyllite clay, as described on the web at:
>  http://www.genhydro.com/pyroclay.html
> It is supposed to slow-release a wide spectrum of nutrient minerals, which 
> should help my otherwise pitiful water to support life.

The same claim could be made for many other clays (even some used in kitty
litter) so I wouldn't get too focused on pyrophillite.

> I am using Natural Gold now, and the improvement over other things I have 
> been trying is minimal at best.  I just got the latest water quality report 
> of inorganic contaminants, and it is amazing what is NOT in my water.
> I'll just say what is---Na 17.6 mg/l ; Flouride 0.35 mg/l ; Sulfate 4.0 mg/l ;
>  Chloride 4.0 mg/l ; Hydrogen Sulfide 0.68 mg/l ; Fe 0.19 mg/l ; Mn 0.14 mg/l 
> ;
> Silica (as SiO2 ) 42.2 mg/l ; Color (whatever that means) 8.0mg/l
> Here's one of those weird things.  Mg is 4.01 mg/l, Ca(as CaCO3) is 26.4 
> mg/l, Hardness(as CaCO3) is 70.7 mg/l, and KH (as CaCO3) is 90.2 mg/l.

I find the hydrogen sulfide to be a little unusual, particularly in the
presence of that much iron.  Your silica is more than 2x "normal" values
and this might cause some false positive readings from phosphate test

> I 
> thought there should be  a closer relationship amongst these readings.  Since 
> Barium is listed as ND (not detectable), I would think that if hardness and 
> alkalinity are both listed in terms of CaCO3, then there should be a very 
> similar reading for all of these things.

You have no noncarbonate hardness (Ca-Mg hardness exceeds alkalinity); the
higher alkalinity is balanced mostly by the sodium.  Barium is usually

> There isn't enough sulfate showing 
> to account for the high alkalinity, and the calcium and magnesium don't add 
> up to the hardness.

Sulfate doesn't contribute to alkalinity.

Calcium and magnesium don't add directly to make Ca-Mg hardness. I
calculate that your hardness should be about 83 mg/l as CaCO3, rather than
70.7 and I can't explain why the difference is that big.  At 83 mg/l your
general hardness and alkalinity would balance a little better.  Here's the
procedure to calculate hardness as CaCO3 from separate calcium and
mangesium concentrations:

1) divide calcium in mg/l by 20 (this gives calcium in milliequivalents
per liter)

2) divide magnesium in mg/l by 12 (this gives magnesium in
milliequivalents per liter)

3) add the milliequivalents of calcium and magnesium

4) there are 50 mg of CaCO3 per equivalent, so multiply your Ca+Mg total
by 50 to get hardness as mg/l CaCO3.

> Strontium isn't listed, could there be that much of it 
> in my water?  The amount of Fe, even if at a plus2 valence, is not enough to 
> get it that high.

Strontium is normally rare or absent.  I don't think that plus2 Fe
registers as hardness - certainly it isn't considered to be part of
hardness.  Maybe someone else would have more to say.

> As for N-P-K, neither potassium nor phosphorus are listed as being or not 
> being detected.  NO3, NO2, and NH3/4 all show as ND, so my fertilizer/plant 
> food needs to be adjusted accordingly.

Whether or not you add any form of nitrogen to your fertilizer should
depend on the nitrogen content in your tanks, not in your tap water, as
feeding will add substantial amounts of nitrogen to your water.

Phosphorus is likely to be low.  With 40+ mg/l of silica in your water you
probably shouldn't bother with a phosphate test kit as silica may
interfere with the phosphate test.

I think a lot of us get a positive response from their plants when they
add potassium.  Unless your K is quite high then you probably will too.

> Now, mind you, some folks on this list keep fish in their tanks for the sake 
> of providing food for the plants.  I, on the other hand am trying to grow 
> plants to keep the nitrates and algae under control, and my fish a Amazon 
> drainage soft-water critters.  This means I don't want to get too much Ca or 
> Mg or CO3 in my tanks, and I would like to keep conductivity down, which may 
> be difficult when providing for the needs of the plants.

If you make a priority out of keeping conductivity low then the idea would
be to use a fertile substrate and add *nothing* to the water that your
plants don't show a specific need for; then when you must add fertilizers,
try to add them to the substrate, not to the water.

Its looks to me like your calcium, magnesium and sodium are well-balanced
so water changes alone are likely to provide the necessary amounts of
calcium and magnesium.  Even the iron is probably adequate for good plant

Even without fertilizer additions, the conductivity of your tank water is 
probably going to rise above the conductivity of the tap because of
evaporation, feeding and other assorted additions to the water.

Roger Miller