Remineralize RO water to a GH and KH

How the product amounts are scaled

Each maker states how many grams give how much hardness in how much water. The calculator scales that straight line to your batch and target. Products that raise GH and KH together do it at a fixed ratio, so you choose the GH and the KH follows; the table tells you where it lands. SaltyShrimp gives its GH to KH ratio as 1 : 0.45 (SaltyShrimp³). Dennerle says 1.5 g per 10 L gives GH 6–7 and KH 1 (Dennerle⁴); we use the 6.5 midpoint. Seachem Equilibrium adds GH only (Seachem¹). For KH it is paired with Seachem Alkaline Buffer, whose label says 6 g per 80 L raises alkalinity by 1 meq/L, or 2.8 dKH (Seachem²).

DIY salts

GH counts calcium and magnesium together. One German degree is 10 mg/L of CaO, which is 0.1783 mmol/L of Ca plus Mg (Wikipedia⁵). One dKH is 0.3567 mmol/L of bicarbonate, twice that, because each bicarbonate ion carries one charge where calcium carries two. From there the grams come from molar masses (IUPAC CIAAW⁶): calcium sulfate dihydrate for calcium, magnesium sulfate heptahydrate for magnesium and potassium bicarbonate for KH. The Ca:Mg ratio is your choice and is labeled as an example.

Shrimp

Dennerle's recommended values for Neocaridina shrimp, the cherry shrimp group, are about pH 7.0–7.5, GH 6–7 and KH about 1 (Dennerle⁴). Adults reach 3–4 cm according to University of Florida IFAS (University of Florida IFAS Extension⁷). Match new water to the tank's water at each change rather than chasing a number.