Hi all,
I'm afraid that the plants can't take up chelated calcium. It can't raise the dGH at all. It's better I stop to add chelated calcium?
Yes stop adding it, sorry I should have made it a bit clearer. When any element is chelated it is unavailable to the plant, this is because it is bound to the chelating compound. Chelators differ from simple chemical salts (like CaCO3 etc), because the ion is bound to the chelating molecule and not combined into it.
Bit about chelates
This bond is often quite stable, and we can only add iron (Fe) as FeEDTA or similar, because although the iron is very tightly held the bond is degraded by sunlight, producing Fe+++ ions, these ions are quite reactive and rapidly form other compounds, many of which are insoluble (e.g. Fe(OH)3). For similar reasons calcium chelates were developed for the food nutritional supplement industry, and are dubiously of value even for that usage.
Raising dGH
If you want to add dGH, any soluble calcium compound (e.g. CaCl2) will add this. If you use "Epsom Salts" MgSO4.7H2O you can raise dGH without adding calcium or adding carbonate hardness, and often a mixture of Epsom salts and calcium chloride is used. Unless you have calcium poor and carbonate (dKH) rich water (very unusual in the UK), you can add a small amount of calcium carbonate to raise both dGH and dKH, the aragonite form of CaCO3 is most soluble, and "Oyster shell chick grit" (sold as a poultry feed supplement) is usually a cheap efficient option.
Plants don't need much calcium, so very small amounts of Ca will do, the same for magnesium, as long as there is some present, you don't need a huge amount.
If you feeI happier with a commercial product, Seachem etc produce salt mixes that raise both dGH/dKH.
cheers Darrel
