[APD] Re: Potassium Bicarbonate in the planted aquarium

["Douglas Guynn" <d_guynn at sbcglobal.net>]

Thanks for the following comments Mr. Purchase.

	"Sulfur IS a macronutrient, although one required in smaller
quantities than the others. Whether or not you could substitute KHCO3 for
K2SO4 in a fertilizer would depend on how much SO4 (Sulfur is apparently
absorbed as SO4) is present in the system already (check your water supply)
and the Alkalinity of your water (CO3 level). If your water is naturally
very, very soft and contains little Alkalinity, you would probably have to
supplement the CO3 level in some way (Baking Soda) if you switch from KHCO3.
It might be possible to go 50-50, using both KHCO3 and K2SO4. Potassium
isn't toxic even at higher levels than really necessary, so you are unlikely
to do any damage, and SO4 is also relatively non toxic at elevated levels
(within reason)."

Well, here's a few of the components in the tap water here that are relevant
to this discussion;

Tot. Alkalinity As CaCO3 - 121 mg/l
Total Hardness as CaCO3 - 571 mg/l
Dissolved solids - 1385 mg/l
Bicarbonate - 148 mg/l
Calcium - 126 mg/l
Chloride - 469 mg/l
Sodium - 263 mg/l
Sulfate - 380 mg/l
I don't know the potassium level.

I dilute this 3 parts RO water to one part tap water because 1.) I don't
like the hard water scale that results from using straight tap water, 2.) I
really enjoy Cardinal Tetras, which seem to do really well in softer water.
That leaves me with the following makeup water for my 75 gallon (280 liter)
tank. I change about 20 gallons of water every week.

Tot. Alkalinity As CaCO3 - 30 mg/l
Total Hardness as CaCO3 - 143 mg/l
Dissolved solids - 346 mg/l
Bicarbonate - 37 mg/l
Calcium - 32 mg/l
Chloride - 117 mg/l
Sodium - 66 mg/l
Sulfate - 95 mg/l

I already add KHCO3 to raise the alkalinity (KH). I don't use NaHCO3 for
this because the sodium level is already elevated. I leave the MgSO4 out of
the PMDD because the water is already harder (GH about 8) than the Cardinals
like.

Do you think adding 7220 mg per week of sulfate (95 mg/l x 76 l) from the
diluted tap water would be enough to keep the plants healthy? Any one know
what the symptoms of sulfur deficiency are?

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