Calcium

Calcium is one of the major ions necessary for successful reefkeeping of SPS corals. In fact, one of the keys to discovering how to keep SPS corals alive in captivity in the late 1980s and early 1990s was an increased understanding of the importance of Calcium and Alkalinity in a closed system.

Calcium is present in natural seawater in relatively high, stable concentrations, but in a closed captive system, it is rapidly depleted. Thats why it is so important to add calcium back on a continuous basis.There are several ways to do this.

How to Replenish Calcium in your Tank

Calcium can be added back through the use of a Calcium Reactor, kalkwasser, or two part supplements that contain Cacium and an Alkalinity such as ESVs Bionic or Kent Marines two Part solution.

Certainly the calcium reactor is the easiest way to maintain adequate levels, but it is also the most expensive to setup initially. However if you are a serious SPS hobbyist, it will make your life easier and lead to greater chance of success.

Calcium ion levels also must maintain a balance with alkalinity at all times. Too much of one can lead to a depletion of the other, upsetting the balance and causing problems with the corals ability to build their stony skeletons

Calcium in Soft Coral Tanks.

Since soft corals dont have a stony skeleton, they dont care about calcium, right?

Wrong.

Soft corals do build a skeleton, its just not continuous. They create calcium carbonate structures called spicules which provide much of the support of their tissues.

They also benefit for the calcium/alkalinity buffering system to maintain stability.

Soft corals are not quite as sensitive to low calcium levels, but its still important to maintain a reasonable level. Many hobbyists have success with 350 ppm and slightly highter Calcium levels. We tend to be around 450 ppm Calcium at our farm, along with 11.2 dkH alkalinity.