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[APD] Re: Nutrient Dosing

Tom Wood asked:

"A few excerpts for the Green Water Treatment Plant (GWTP)

In mg/L

Calcium 12

Magnesium 15

Total Hardness (as CaCO3) 93

Total Alkalinity 66
(as CaCO3)
Can some of the chemists here decipher what this means? I don't add Magnesium, but should I?"

You don't need to add either Calcium or Magnesium nor adjst the Alkalinity given those readings. You do know that the reported results as CaCO3 doesn't necessarily mean that CaCO3 is the sole diatomic cation responsible for the water's hardness. Any +2 cation will contribute to water hardness, but Ca+2 and Mg+2 are the most common. The readings are reported as ppm (mg/l) CaCO3 purely as convention.

"My newly planted H. difformis has white veins and rather spindly new growth. The new leaves also don't have the deeply cut ridges characteristic of this plant. I'm assuming Fe deficiency here, since the iron was nearly undetectable when the plants first went in. Current iron levels are at 0.1 ppm."

Try cranking up the Fe levels. Are you using a balanced micronutrient mix or dosing iron by itself?

"My h. difformis started doing better when I cut back on K2SO4, but I'm not sure of a connection."

I doubt that K2SO4 was a problem. Potassium is relatively benign as is SO4. Both Potassium and Sulphur are macronutrients and they don't usually cause much of a problem if present slightly in excess of the plant's needs.

How is your lighting and CO2 levels?

James Purchase

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