hw® supplementing salts
Use hw® supplementing salts to adjust calcium, magnesium and carbonate hardness to the measured needs of your marine aquarium.
Combined salt additions also affect ionic ratios and salinity. In the Balling method, a sodium-chloride-free marine salt mix supplies the other salt components. Monitor salinity as well as the individual water parameters and compensate for an increase in a controlled way during aquarium maintenance.
The following instructions describe the use of the individual hw® salts. Observe the specified combinations and dissolve the components of the three-container method separately.
hw® Calcium Chloride Dihydrate
CaCl₂ · 2H₂O
Powdered calcium chloride for adjusting water parameters
Pure calcium chloride dihydrate for adjusting calcium levels as part of combined calcium chloride and sodium bicarbonate dosing.
General procedure
This method supplies calcium and carbonate hardness by adding hw® Calcium Chloride Dihydrate (CaCl₂ · 2H₂O) and hw® Sodium Bicarbonate (NaHCO₃). Sodium and chloride remain as additional sodium chloride (NaCl), which can gradually alter the seawater composition.
The sodium-chloride-free salt mix hw® MineralMarin supplies the other marine salt components. Salinity also rises gradually with this method. Monitor it regularly, taking temperature into account when using a hydrometer, and compensate for the increase during water changes.
hw® Magnesium Chloride Hexahydrate
MgCl₂ · 6H₂O
Fine-crystalline magnesium chloride for adjusting water parameters
Pure magnesium chloride hexahydrate for adjusting magnesium levels as part of combined magnesium chloride and sodium bicarbonate dosing.
General procedure
This method supplies magnesium and carbonate hardness by adding hw® Magnesium Chloride Hexahydrate (MgCl₂ · 6H₂O) and hw® Sodium Bicarbonate (NaHCO₃). Sodium and chloride remain as additional sodium chloride (NaCl), which can gradually alter the seawater composition.
The sodium-chloride-free salt mix hw® MineralMarin supplies the other marine salt components. Salinity also rises gradually with this method. Monitor it regularly, taking temperature into account when using a hydrometer, and compensate for the increase during water changes.
The principle
Magnesium is an important component of natural seawater and is consumed by biological processes in the aquarium. Adjust the magnesium level as needed to prevent a deficiency. The reference range given here for natural seawater is 1250–1380 mg/l, with seasonal and geographical variation.
Use hw® Magnesium Chloride Hexahydrate together with a precisely measured amount of hw® Magnesium Sulfate Heptahydrate to avoid an unfavourable change in the chloride-to-sulfate ratio.
General procedure
The quantities account for molar masses, water of crystallisation and the chloride-to-sulfate ratio. Use the following combination to supply 1.00 g of magnesium:
- 0.95 g hw® Magnesium Sulfate Heptahydrate (MgSO₄ · 7H₂O)
- 7.58 g hw® Magnesium Chloride Hexahydrate (MgCl₂ · 6H₂O)
Example
A marine aquarium containing 500 l of water has a magnesium level of 1200 mg/l. Raising it to 1300 mg/l requires an additional 100 mg/l × 500 l = 50 g of magnesium.
- 50 g × 0.95 = 47.50 g hw® Magnesium Sulfate Heptahydrate
- 50 g × 7.58 = 379.00 g hw® Magnesium Chloride Hexahydrate
Dissolve both salts together in 600 ml of reverse osmosis water, then make up to 1000 ml. Add 100 ml per day over the next 10 days. Check the aquarium magnesium level on day 5 and adjust if necessary.
hw® Sodium Bicarbonate
NaHCO₃
Powdered sodium bicarbonate for adjusting carbonate hardness
Pure, fine-crystalline sodium bicarbonate supplies carbonate hardness as part of combined supplementation with calcium chloride or magnesium chloride. Calcium or magnesium is supplied by the corresponding chloride component.
General procedure
This method supplies calcium and carbonate hardness by adding hw® Calcium Chloride Dihydrate (CaCl₂ · 2H₂O) and hw® Sodium Bicarbonate (NaHCO₃). Sodium and chloride remain as additional sodium chloride (NaCl), which can gradually alter the seawater composition.
The sodium-chloride-free salt mix hw® MineralMarin supplies the other marine salt components. Salinity also rises gradually with this method. Monitor it regularly, taking temperature into account when using a hydrometer, and compensate for the increase during water changes.
General procedure
This method supplies magnesium and carbonate hardness by adding hw® Magnesium Chloride Hexahydrate (MgCl₂ · 6H₂O) and hw® Sodium Bicarbonate (NaHCO₃). Sodium and chloride remain as additional sodium chloride (NaCl), which can gradually alter the seawater composition.
The sodium-chloride-free salt mix hw® MineralMarin supplies the other marine salt components. Salinity also rises gradually with this method. Monitor it regularly, taking temperature into account when using a hydrometer, and compensate for the increase during water changes.
hw® Magnesium Sulfate Heptahydrate
MgSO₄ · 7H₂O
Fine-crystalline magnesium sulfate for adjusting water parameters
Pure magnesium sulfate heptahydrate for adjusting magnesium levels in combination with hw® Magnesium Chloride Hexahydrate.
The principle
Magnesium is an important component of natural seawater and is consumed by biological processes in the aquarium. Adjust the magnesium level as needed to prevent a deficiency. The reference range given here for natural seawater is 1250–1380 mg/l, with seasonal and geographical variation.
Use hw® Magnesium Chloride Hexahydrate together with a precisely measured amount of hw® Magnesium Sulfate Heptahydrate to avoid an unfavourable change in the chloride-to-sulfate ratio.
General procedure
The quantities account for molar masses, water of crystallisation and the chloride-to-sulfate ratio. Use the following combination to supply 1.00 g of magnesium:
- 0.95 g hw® Magnesium Sulfate Heptahydrate (MgSO₄ · 7H₂O)
- 7.58 g hw® Magnesium Chloride Hexahydrate (MgCl₂ · 6H₂O)
Example
A marine aquarium containing 500 l of water has a magnesium level of 1200 mg/l. Raising it to 1300 mg/l requires an additional 100 mg/l × 500 l = 50 g of magnesium.
- 50 g × 0.95 = 47.50 g hw® Magnesium Sulfate Heptahydrate
- 50 g × 7.58 = 379.00 g hw® Magnesium Chloride Hexahydrate
Dissolve both salts together in 600 ml of reverse osmosis water, then make up to 1000 ml. Add 100 ml per day over the next 10 days. Check the aquarium magnesium level on day 5 and adjust if necessary.
Tips
Preparing solutions and using supplementing salts with different methods
Calcium supplementation using the Balling method
Calcium chloride and sodium bicarbonate supply calcium and carbonate hardness. The additional sodium and chloride affect the ionic balance; sodium-chloride-free hw® MineralMarin complements the other salt components. Monitor salinity regularly and compensate for its gradual increase during water changes.
Preparing the solutions
Prepare the three solutions in separate containers. For each container, dissolve the following quantity in 2 litres of reverse osmosis or distilled water:
- Container I: 213.50 g hw® Calcium Chloride Dihydrate
- Container II: 163.80 g hw® Sodium Bicarbonate
- Container III: 48.75 g hw® MineralMarin
Using the solutions
With this combined method, raising calcium by 50 mg/l corresponds to an increase in carbonate hardness of about 7 °dKH. Initially add 5 ml of each solution per 10 litres of aquarium water and measure calcium and carbonate hardness daily.
Raise both values slowly. Once the desired values have been reached, adjust the dose up or down in steps of about 10% until the values remain stable. Continue regular testing, generally at least weekly. Seasonal changes and changes in livestock or growth can alter consumption and require a different dose.
Magnesium and carbonate supplementation
The principle follows the calcium method, but container I contains magnesium chloride instead of calcium chloride. Prepare the solutions separately using the following amounts per 2 litres of reverse osmosis or distilled water:
- Container I: 199.20 g hw® Magnesium Chloride Hexahydrate (MgCl₂ · 6H₂O)
- Container II: 163.80 g hw® Sodium Bicarbonate
- Container III: 48.75 g hw® MineralMarin
Follow the dosing procedure described for the calcium method. Magnesium consumption is usually much lower than calcium consumption. A one-off correction may therefore be sufficient, with a measurable decline only becoming apparent after weeks or months.
Avoid excessive magnesium levels. The guidance given here warns against values above 1600 mg/l; repeated water changes may be needed to return to the stated reference range of 1250–1380 mg/l.
All supplementing salts
Explore all supplementing salts in our product catalogue.
Information and tips for marine and freshwater aquariums
UV-C radiation
Reverse osmosis
