CALCIUM Submitted By Gary V. Deutschmann, Sr. Reef And Invert Aquarium Resources

(Gary is the inventor of the denitrifying product AZ-NO3)

Calcium, a metallic element, symbol Ca, was so named by Sir Humphry Davy because of its occurrence in chalk (q.v.) Calcium does not occur in the free state, but compounds of the element are widely distributed. In the earth's crust calcium is the fifth most abundant element; it constitutes 3.63% of the igneous rocks and 3.22% of the entire crust of the earth.

In 1808 Davy showed that lime was an oxide of the metal which he named calcium. Robert Bunsen electrolyzed calcium chloride, and A. Matthiessen obtained the metal by the electrolysis of a mixture of fused calcium and sodium chlorides. While calcium was formerly produced by electrolysis of anhydrous calcium chloride, practically all commercial production is by the reduction of lime by aluminum in heated retorts under low pressures. Calcium distills out of the reaction mass and is collected in a cool section of the retort or in a condenser.

Calcium is one of the alkaline-earth metals of Group II of the periodic table. It is a silvery-white metal when freshly prepared, but it reacts readily with oxygen and nitrogen and tarnishes when exposed to the air to produce a gray and slightly yellow surface.

There are six stable isotopes of the element, however, I will only discuss those of relevance to the aquarium hobby.

In general, the compounds of calcium resemble those of strontium and barium but are, with a few exceptions, somewhat more soluble in water. (The exceptions are; carbonates, hydroxides, oxides and phosphates.) Calcium hydride, CaH2, sometimes called hydrolith, is obtained by heating the metal in a current of hydrogen. This compound is easily transported and on treatment with water yields hydrogen. The remaining calcium forms the monoxide CaO, the peroxide, CaO2, and possibly a tetroxide, CaO4. The monoxide is commonly called lime (q.v.) or quicklime and the corresponding hydroxide, Ca(OH)2, which is sometimes called slaked lime, or in our hobby, kalkwasser (the German name for hydrated lime).

Calcium hydroxide is an inexpensive alkaline substance. It is not very soluble in water. In industry, it is generally used in the form of a suspension of the solid in water called milk of lime, for eg. in mortar or plaster, where as the material dries, the hydroxide is slowly converted into calcium carbonate by the action of carbon dioxide in the atmosphere.

Calcium hydroxide (kalkwasser) is one of the primary sources of calcium in the reef aquarium. The solubility of Calcium hydroxide in 2 megohm triple distilled lab grade water is Ksp 8.70 x 10-9 (-9 superscript), considerably less in water that is not as pure. In plain language, that equates to approximately 35% by volume of Ca(OH)2 is soluble, the remaining insoluble calcium reacts with carbon dioxide CO2 in the water to form the carbonate, CaCO3, which as a suspension will fall out of solution to the bottom of the container or aquarium.

Calcium hydroxide for reef aquarium use should be prepared in a glass or lead-free ceramic glazed container. The amount of the hydroxide placed in the container is not critical, the solution cannot be saturated more than 100%, as a rule of thumb, most aquarists start with 1 tablespoon of calcium hydroxide in 1 gallon of water. After they decant only the clear liquid, the hydroxide is replenished in 1 teaspoon increments at each usage. The solution is replaced periodically as the carbonate takes on a tan or beige appearance.

As the clear decant of CA(OH)2 is 100% saturated, the aquarist should add to the dosing device approximately 1% pure water before filling the device with the solution. This partially eliminates the film and deposition of CaCO3 on the walls of the container, from evaporation. The use of the suspension of solids (milk of lime) is not recommended, as it does not aid in increasing the Ca levels of the aquarium, and over time, can lead to CaCO3 buildup within the substrate. Many aquarists have already noticed that more than half of the clear decant appears as solid calcium carbonate formations within the dosing area of the aquarium or sump. The reason for this is aquarium water already contains minerals in suspension, thus it cannot hold the super-saturated decant of calcium hydroxide as dosed and the overage is precipitated out of solution almost immediately upon being introduced to the aquarium as calcium carbonate.

Anhydrous calcium chloride can be used on occasion, to help boost Ca levels back up to the range you desire. Then the clear decant of calcium hydroxide should be utilized to help maintain these levels. In most situations, the Ca levels will fall slowly over time and require another boost of the anhydrous calcium chloride to return to the range desired. Always use anhydrous calcium chloride with care and sparingly, its overuse can be disastrous to your aquariums inhabitants.

There are numerous other sources of concentrated Ca to raise Calcium levels to the desired range just as effectively, most of these are proprietary and sold under the various manufacturers trade names. The dosing instructions are normally stated clearly on the label. These products should be utilized first, if at all possible, before using the different grades of anhydrous calcium chloride available.

The use of calcium/carbon dioxide, CO2 reactors, wherein the calcium carbonate, CaCO3 is utilized to raise calcium levels in the aquarium, although efficient, is recommended only for experienced aquarists, or those that have the necessary controllers or test equipment to continually monitor CO2 levels in their aquariums. CO2 is a gas that readily mixes with your aquarium water to form carbonic acid. The carbonic acid can be in the bound or in the free form, free CO2 will drive pH down, unless adequate buffers are present to maintain a high dKH level.

Submitted By Gary V. Deutschmann, Sr. Reef And Invert Aquarium Resources

More information on Kalkwasser

Mixing Kalkwasser Add approx 3/4 to 1 teaspoon per gall mix it for a few hours Let it sit for 4 to 6 hours Without disturbing the sediment in your mixing vessel add the upper portion of water rinse the vessel and discard the sediment Also, how much should I start off with, considering I will be adding it daily? Use it for ALL your make up water (evaporation)

What is the most commonly used additive?

The additive I use most regularly is Kalkwasser aka:calcium hydroxide this is mixed and added for evaporation (makeup water) usually weekly. The only other two products are iodine and strontium, added bi-weekly in between waterchanges. IMO, using a high quality salt mix i.e.: coralife mixed with purified tap water will replace the complex needed trace elements. Water changes done on a regular basis either 2 3 or 4 week intervals are important. The more frequent WC and maintenance schedule (vacuuming the live rock)will usually result in optimum conditions for the rock and live stock. Some reefkeepers will try and by-pass the water changes by simply adding a wide range of trace elements. I doubt if this can be done with any certainty.

What does pickling lime do for the reef tank? Pickling lime is food grade calcium hydroxide. What it does is elevate pH and maintain calcium.

After checking all the stores in my area... Super Kmart, Super SandS, Big Y, etc..etc..etc I've have not been able to locate this lime. I called Altrista Corp. makers of Ball products and they were happy to send it to me. Costs 16oz $1.30 or a 12 pk(master canner) for $14.20 + $6 for shipping.$20.28 for 12 lb. I told the woman she could be expecting a flood of calls ;-) 1-800-240-3340 she says "that’s what I'm here for". They are in Muncie Indiana (apparently the canning capital of the nation)

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