Calcium Level

The calcium level in your reef aquarium is considered by many as a critical parameter that should be maintained between 380 to 450 ppm.

Many corals need calcium to form their skeletons which are composed primarily of calcium carbonate. As they grow, the calcium level in your tank will diminish. If levels go below 360 ppm the corals cannot get enough calcium and their growth will slow down and can even stop.

For low and medium demand systems, regular water changes with a good salt mix should be sufficient enough to add the necessary calcium back into your reef.

If you have a high demand tank with sps and/or clams, you will probably need to supplement the calcium. There are a few ways to do this.

Many hobbyists use limewater (kalkwasser) to add calcium to their aquariums. One such method is to replace all evaporated water with kalkwasser (limewater). Since evaporation rates stay pretty constant, they are in reality adding the same amount of calcium all the time.

There is one problem with the above method. As your tank ages, the demand for calcium is going to rise. Even coralline algae require calcium to grow. If you continue to add the same amount of supplement, it will not be sufficient.

A calcium reactor is a device that dissolves calcium carbonate in a reactor chamber, and then drips it into a reef aquarium. The reactor chamber is filled with calcium carbonate granules and sealed. Water is pumped into the chamber and recirculated through the media using a recirculating pump. CO2 is injected into the reactor chamber, which lowers the pH of the recirculating water. At the lower pH (between 6.5 and 6.8), the calcium carbonate dissolves and turns into various components, the main one being calcium and another is carbonates. This drip from the reactor is rich in calcium and rich in buffer.

Although a calcium reactor is initially rather expensive, over time it will be a lot easier, requiring much less time than adding supplements every day. It is also a more accurate method to keep your calcium levels stable.

I would recommend a calcium reactor for anyone that has a high demand system.