CaCl2 Calcium Chloride Remineralise Guide: RO Shrimp Water
Crystal red and Taiwan bee shrimp keepers in Singapore who run RO water need to put minerals back in before the water hits the tank, and calcium is the single ion that makes or breaks moulting success. This cacl2 calcium chloride remineralise guide from Gensou Aquascaping at 5 Everton Park covers when CaCl2 makes sense versus all-in-one GH boosters, the recipe maths for typical shrimp targets, and the calcium-to-magnesium ratios that produce healthy moults rather than stuck shells. Calcium chloride is cheap, dissolves cleanly and gives precise control over remineralised water chemistry.
Why Standalone Calcium Sometimes Wins
Most shrimp keepers reach for all-in-one boosters like Salty Shrimp GH+ or Mosura Mineral Plus, which pre-mix calcium, magnesium and trace salts at a balanced ratio. These products are excellent for daily-use simplicity. Standalone CaCl2 enters the picture when you want to fine-tune calcium without disturbing other ions, when troubleshooting moulting issues, or when running custom water blends for breeding programmes. It is the precision tool versus the all-in-one paintbrush.
The Chemistry of Calcium Chloride
Anhydrous CaCl2 is 36.1 percent calcium by weight; the more common dihydrate (CaCl2·2H2O) is 27.3 percent. Aquarium and food-grade products usually ship as the dihydrate. One gram of dihydrate dissolved in 100 litres raises Ca by approximately 2.7 ppm. For a 60 litre RO blend wanting +20 ppm Ca, you need roughly 4.4 grams. Always check the form (anhydrous vs dihydrate) on your bag because the contribution differs by a third.
Stock Solution Recipe
Dissolve 200 grams of CaCl2·2H2O in 500 ml of distilled or RO water. CaCl2 is hygroscopic and exothermic on dissolution; the bottle warms perceptibly when mixing. Add salt slowly while stirring to avoid splash burns. The solution clears within minutes. Store in opaque HDPE; the solution is stable indefinitely but absorbs CO2 from air over months, slightly reducing potency. Mark the bottle clearly. From a 400 g/L stock, 1 ml delivers 0.4 grams of dihydrate, raising Ca in a 60 litre tank by approximately 1.8 ppm.
Calcium Targets for Shrimp Water
Crystal red Caridina thrive at Ca between 20 and 35 ppm. Neocaridina tolerate higher (40 to 60 ppm). Wild-type Sulawesi cardinals want Ca toward 50 ppm with high pH. For a typical Caridina blend targeting GH 5 to 6, calcium contribution should be around 25 to 30 ppm, with magnesium covering the rest of the GH at 8 to 10 ppm in a 3:1 ratio. The aquarium tds explained for shrimp keepers piece covers the broader TDS context.
The Ca:Mg Ratio That Matters
Shrimp shells form from calcium carbonate but require magnesium for the enzymatic processes that drive moulting. A 3:1 Ca:Mg ratio by ppm is the classic target; ratios closer to 1:1 cause soft shells, and ratios exceeding 5:1 cause stuck moults. To hit 30 ppm Ca and 10 ppm Mg in a 60 litre RO blend, dose 6.6 grams CaCl2·2H2O and 6 grams MgSO4·7H2O. The aquarium calcium magnesium guide walks through the maths in detail.
Mixing RO for Shrimp From Scratch
Start with cold RO water at 0 ppm TDS in a clean bucket. Add Epsom for magnesium first, stir until dissolved. Add CaCl2 next, stirring continuously to avoid local supersaturation. Add a pinch of KCl or potassium sulphate for trace potassium, then any GH-booster supplements. Allow to settle for 30 minutes, test TDS and GH, adjust if needed, then change. Pre-mixing 24 hours before use stabilises temperature and dissolved gases.
Sourcing CaCl2 in Singapore
Food-grade CaCl2 dihydrate is sold for cheese-making at certain Tekka Centre and Sungei Road shops at $8 to $12 per kilogram. Industrial dehumidifier CaCl2 from Horme costs $5 per kilogram but check the food-grade designation; some industrial stocks include anti-caking additives unsuitable for tanks. Aquarium-branded calcium pouches at C328 and Polyart cost $15 to $20 per 250 grams. The bulk food-grade source is dramatically better value.
Avoiding the Chloride Trap
CaCl2 contributes both calcium and chloride. Heavy or sustained dosing pushes chloride above 30 ppm, where sensitive Caridina start to show stress. For tanks where Ca needs significant supplementation, alternate CaCl2 with calcium carbonate (CaCO3, ground oyster shell) which contributes only Ca and CO3. Pure CaCl2 use is fine for occasional remineralising; for daily dosing in a closed system, mix with CaCO3 to keep chloride manageable.
Dosing for Water Changes
Most Caridina keepers do 10 to 20 percent weekly water changes. For a 60 litre tank doing 10 litre weekly changes with RO + remineralised water, dose 1.1 grams CaCl2·2H2O and 1 gram Epsom into the change water before adding to the tank. This maintains Ca at 30 ppm and Mg at 10 ppm if your existing tank water is already at target. Add the remineralised water slowly to avoid shrimp stress from temporary localised salinity spikes.
Plants, Tests and What You Actually Dosed
Crypt and Buce species in shrimp tanks tolerate the soft, low-calcium water but show better leaf integrity at Ca above 20 ppm. CaCl2 dosing for shrimp incidentally feeds the plants, which is a happy alignment. Heavy stem plants in shrimp tanks rarely thrive because the dosing routines for plants and shrimp pull in different directions; choose one focus per tank. The aquarium calcium deficiency plants guide covers the plant side.
API GH kits cannot distinguish Ca from Mg, so a “GH 6” reading after CaCl2 dosing does not confirm calcium reached target. Salifert and Hanna both sell dedicated calcium test kits priced around $25 to $35 in SG. The Salifert kit reads in 10 ppm increments, sufficient for shrimp work. Test new water blends weekly during the first month, then monthly once your recipe stabilises.
Sample Recipe for 20 Litres of Crystal Red Water
Take 20 litres of fresh RO water at 0 TDS. Add 2 grams of MgSO4·7H2O, stir to dissolve. Add 2.2 grams of CaCl2·2H2O, stir to dissolve. Add 0.2 grams of K2SO4 for potassium. Test: target TDS around 100 to 130 ppm, GH 5 to 6, calcium 25 to 30 ppm, magnesium 8 to 10 ppm. Allow to sit overnight before water change. Pair the routine with the maintenance discipline in our aquarium water change guide.
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