API® Marine Calcium is crucial for maintaining the calcium levels in a reef aquarium, which is essential for the health of corals and other calcium-dependent organisms. Here's a quick overview of when and how to use it:

• Purpose: Calcium is vital for coral growth and health, as it helps facilitate the formation of calcium carbonate structures. Low calcium levels can lead to poor growth and health of corals.

• Usage: You should use API Marine Calcium when your water tests show calcium levels below 400 ppm (mg/L). It's important to regularly test your water to monitor calcium levels, as maintaining optimal levels is essential for a thriving reef environment.

• Application: Follow the manufacturer's instructions for dosage based on your aquarium's size and the current calcium level. Gradual adjustments are preferable to avoid shocking the system.

If you're unsure about how to test calcium levels or have questions about dosage and application, feel free to ask for more guidance!