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Thought I would run this question by the APD Think Tank before I really
messed things up. In order to keep it clear in my head, I am going to use
terms different than some on this list may not be accustomed to, so please
forgive me if it causes any confusion.

My tap water has the following parameters;
	Total alkalinity (as CACO3) - 121 mg/L (about 7 kH)
	Total hardness (as CACO3) - 571 mg/L (about 32 dH)
	Calcium - 126 mg/L
	Magnesium - 62 mg/L

I add PMDD using 24/7 injection of an extremely dilute solution. This not
only accomplishes the nutrient addition, but compensates for evaporation,
maintaining the water level in the tank without having to perform constant
top-offs (It requires about 60 mls/hour to maintain the water level in the

My desire is to populate the tank with a large school of Cardinal Tetras. I
understand they prefer soft water. I am told this refers to hardness, not
alkalinity. I lower the hardness some by doing water changes with one part
tap water diluted with 2 parts RO water. I occasionally add potassium
bicarbonate to maintain acceptable alkalinity levels (tap water sodium
levels are also very high).

Wouldn't it be a good idea to omit the MgSO4 from the PMDD stock solution?
The hardness is already high enough, and the Mg only aggravates the
condition. The SO4 lost using practice could be made up by additional K2SO4

Any comments?

Douglas Guynn, in far west Texas, wishing we could get some of the rain from
the east coast.

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