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Calcium In Your Reef Tank

Calcium is an element that is truly vital for life, not just on the reef, but in all living creatures including us. We cannot grow our skeletons without it, our hearts cannot beat without it and our muscles cannot function without it. In this blog we shall discuss Calcium's role in the reef aquarium, as well as the importance of maintaining calcium levels for long term aquarium health.

Calcium In Aquarium Water

For us Aquarium Keepers, Calcium is one of the main essential elements providing the building blocks in your reef aquarium. It is used consistently by Corals and other organisms through a process called calcification.

Calcium Binds with Alkalinity to form Calcium Carbonate which is used to make up the skeleton in Stony corals; as well as the shells and structures of other organisms in your reef. Montipora Capricornis

Ideal Levels?

400-450ppm

(In-store we aim for 420ppm in our Coral systems)

While Preferred Calcium levels vary dependant on people's individual opinions it is clear that too little or too much Calcium can unbalance the reef equilibrium and spell disaster for certain tank inhabitants. So How much is too Little?

If we take a look at Natural Sea Water (NSW) We can see that All over the world this averages around 410ppm of Calcium. This in itself shows us that coral growth and reef Calcification is optimal at these levels on the largest scale.

If your aquarium drops below 400ppm the availability for your corals becomes too little and many Stony Corals will start to bleach (lose colour) and possibly perish at these levels.

So why does the range vary so much?

In order to answer this in full the aquarium must be monitored with more than just Calcium in mind. Alkalinity and Magnesium levels also play a huge role in the stability of Calcium.

Higher Calcium levels (450-500) can increase the growth of Stony corals rapidly however growth can become fragile, with thin skeletons, and corals grown in these conditions often lacks intense colouration.
When adjusting your Calcium it is often the case that your Alkalinity level will Counteract as if on a seesaw. One goes up the other down. So when trying to get an optimal level it is the art of balancing both of these parameters.
If your aquarium is heavily stocked and using Calcium at a rapid rate you may opt for higher levels to provide a comfort blanket incase of a sudden drop.

How to supplement?

Once the level of aquarium Calcium is know, dosing MUST take into account the total volume of water in the aquarium, the Alkalinity level and the Magnesium level. When Calcium is added to the water column it immediately counteracts Alkalinity levels, the same is true in reverse. It is important therefore to ensure the Alkalinity is above the recommended level, usually 8.3 dKH, before dosing Calcium.

Science behind the Coral Skeleton

The process by which coral skeletons are formed is known as biomineralization, which is facilitated by specialized cells within the coral polyp called Sclerocytes. Sclerocytes secrete a matrix of proteins and other organic molecules that serve as a scaffold for the deposition of calcium carbonate crystals, and it's out of this chemical brickwork that the skeleton is constructed.

Common Questions

Why doesn't my aquarium use Calcium?

This can be down to either a low coral load or a lack of available magnesium. Magnesium increases the availability of all essential elements to corals, and a low level can cause Calcium to combine with Alkalinity constituents to form Calcium Carbonate outside the corals. The recommended level of Magnesium is around 1350-1500ppm.

Why does my Magnesium go up when I dose Calcium?

Both Calcium and Magnesium are Alkaline Earth Metals from Group 2 of the Periodic Table. As such their chemical properties are very similar, with the same particle size and the same Ionic 2+ Charge. As a result, many Calcium supplements will have Magnesium in them as well, despite the refining process removing most of it.

Random Fact

You may have heard of Coral reefs being destroyed over the years due to climate conditions and over fishing but did you know that there are projects that are successfully rebuilding them at astonishing rates. Through the power of electrolysis we are now able to speed up coral growth by up to 400% in stony corals; The electric current causes calcification to increase significantly so we can build new reefs for a quarter of the time!