Shrimp keepers building water from RO or distilled water need to add minerals back precisely, because both too little and too much TDS stress sensitive caridina and neocaridina. This calculator turns your starting TDS, target, and volume into an exact remineralizer dose in grams, so each water change lands on the same parameters.
How it works
The dose follows directly from how much you need to raise TDS and how strong the product is:
rise needed = target TDS − starting TDS
grams = rise needed × volume(L) / dose strength
dose/L = grams / volume(L)Dose strength is the ppm of TDS each gram raises in one litre, taken from the product spec. Because remineralizer only adds dissolved solids, the rise must be positive — if your target is lower than the current TDS, the only way down is to dilute with more pure water.
Example and tips
Mixing 20 L of RO water at 0 ppm up to 130 ppm for a caridina tank, with a GH+ salt that raises about 100 ppm per gram per litre, needs roughly 26 grams total, or 1.3 grams per litre. Always add the remineralizer to a mixing container first, stir until fully dissolved, let it settle a few minutes, then confirm with a TDS pen before the water goes into the tank — different salts and batches vary, so the meter is the final word.