|Unit(s):||1 ppm ~ 1 mg/l|
|Target:||400 - 450 ppm|
|Danger:||< 200 ppm|
Calcium (along with alkalinity) is an important element in any marine aquarium where calcareous organisms are present. These are organisms that secrete calcium carbonate and include:
- coralline and other calcareous algae
- clams and other bivalves
- stony corals
- most soft corals
- some tubeworms
Normal seawater has a calcium concentration of around 420 mg/L and the ideal concentration in a marine aquarium should be around this number or slightly higher.
The easiest way to maintain calcium (and alkalinity) in an aquarium is to replace evaporated water with kalkwasser. This involves dissolving calcium hydroxide in water which is then added slowly to the system via a drip, peristaltic pump, or float valve system. This can also be added using a calcium hydroxide reactor.
For aquaria with a higher demand for calcium and alkalinity, a calcium carbonate reactor can be used. This uses carbon dioxide to lower the pH of the water that enters the reactor, which then dissolves the calcium carbonate substrate. This effluent which is enriches in calcium and alkalinity in the correct ratio is then returned to the system.
It is also possible to adjust calcium levels directly by using calcium chloride or similar products. It is available in various specific commercial aquarium preparations such as Kent Marine Turbo-Calcium. While not strictly calcium chloride, Seachem Reef Calcium servers the same purpose. Damp Rid which can be purchased in most supermarkets is also calcium chloride. Some commercially available produces have the additive already dissolved in water. While this may be convenient, it is a very expensive way to maintain levels.
Long term use of the calcium chloride products should be avoided as they not only add calcium but chloride (or some other anion) which will accumulate without regular water changes. Kalkwasser and calcium carbonate reactors add nothing else but calcium and alkalinity so are called balanced additive techniques.
- Reef Chemistry Calculator - This page is designed to calculate reef chemistry additions for calcium or alkalinity using commercial products or standard chemicals.
- Calcium by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
- An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - reefkeeping.com
- Electronic Calcium Monitoring by Randy Holmes-Farley - reefkeeping.com
- Solving Calcium and Alkalinity Problems by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
- When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - reefkeeping.com
- Calcium and Alkalinity by Randy Holmes-Farley - reefkeeping.com
- How to Select a Calcium and Alkalinity Supplementation Scheme by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
- A Homemade Two-Part Calcium and Alkalinity Additive System by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
- Purity of Calcium Chloride by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
- Calcium Carbonate as a Supplement (Aragamight; Liquid Reactor) by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
- Simulating the Effect of Calcium Chloride and Sodium Bicarbonate Additions on Reef Systems by Craig Bingman - Aquarium Frontiers
- Additional Simulations: The Combined Effect Of Calcium Chloride/Sodium Bicarbonate Additions And Water Exchanges by Craig Bingman - Aquarium Frontiers