How magnesium level affects the growth and health of corals

Table of Contents

Magnesium (Mg) is a key element in marine ecosystems, playing an essential role in the calcification process, which is fundamental for the growth and health of corals.


Calcification is the process by which corals and other marine organisms produce calcium carbonate (CaCO3), creating their skeletal structures. The impact of magnesium on this process is multifaceted and crucial for maintaining the proper conditions in marine aquariums.

Role of magnesium in calcification

Coral calcification involves precipitating calcium carbonate from seawater to build the skeleton. Magnesium plays several key roles in this process:

Stabilization of calcium ions: Magnesium competes with calcium ions for places on the surface of calcium carbonate crystals, preventing too rapid precipitation of calcium carbonate and the formation of overly large crystals. This makes the calcification process more controlled and efficient. Magnesium ions block certain sites on the surface of growing crystals, resulting in slower and more controlled growth of these crystals.

Without magnesium, calcium ions could adhere more quickly and in larger amounts to the surface of crystals, potentially leading to the formation of irregular and weaker structures. Magnesium thus acts as a “regulator,” ensuring even and stable precipitation of calcium carbonate, which is essential for building durable and healthy coral skeletons.

Impact on pH and alkalinity: Magnesium helps stabilize the pH and alkalinity of seawater, which is key for the calcification process. Optimal pH and alkalinity conditions ensure that corals can effectively precipitate calcium carbonate.

Impact of magnesium on coral health  

Skeletal structure: An adequate level of magnesium in seawater ensures that corals can form strong and healthy skeletons. A deficiency in magnesium can lead to weakened skeletal structure, making corals more susceptible to mechanical damage and environmental stress.

Metabolic processes: Magnesium is also crucial for many metabolic processes in coral cells, including protein synthesis and enzyme function. A deficiency in magnesium can disrupt these processes, affecting the overall condition and health of the corals.

About the author

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Marek Protasewicz

Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.

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