Coral Tank KH and Calcium Management | How to Use Additives
This article explains the relationship between KH, calcium, and magnesium essential for coral skeletal formation, as well as management methods such as two-part additives, kalkwasser, and reactors.
Key Takeaways
This article explains the relationship between KH, calcium, and magnesium essential for coral skeletal formation, as well as management methods such as two-part additives, kalkwasser, and reactors.
In the keeping of stony corals (LPS and SPS), management of KH (alkalinity) and calcium is an especially important element of water quality management. Because corals take in calcium carbonate from seawater to form their skeletons, when these values decline, growth stops, and in the worst case their skeletons can dissolve. This article explains the relationships between KH, calcium, and magnesium, as well as concrete methods for adding and managing them.
The Relationship Between KH, Calcium, and Magnesium
These three elements are closely related, and managing only one will not produce results.
| Item | Role | Natural Seawater Value | Aquarium Target |
|---|---|---|---|
| KH (Carbonate Hardness) | An indicator showing the total amount of carbonate and bicarbonate ions in seawater. Corals bind these ions with calcium ions to form calcium carbonate (CaCO3) skeletons | Approximately 7 dKH (125 ppm) | 7–11 dKH (approximately 8–9 dKH is ideal to promote active SPS growth) |
| Calcium (Ca) | The direct material that combines with KH to form skeletons | Approximately 420 ppm | 400–450 ppm |
| Magnesium (Mg) | A "mediator" that prevents the precipitation of calcium carbonate | Approximately 1280 ppm |