Aquarium Fish

Trace Elements and Supplements

posted: 05/15/12

The inhabitants of almost any saltwater aquarium require supplements added to the water. The type of supplements depends upon the type of inhabitants, as shown below. The trace elements of special concern for reef tanks include calcium, iodine, and strontium.

Marine Aquarium Containing: Small or Large Polyp Stony Corals, Giant Clams, Leather Corals, Polyps, Mushroom Anemones

- Calcium: Helps build skeleton

- Iodine: Helps prevent damage due to excessive light exposure

- Strontium: Helps build skeleton

- Magnesium: Helps prevent premature calcium precipitation

- Buffer (Alkalinity): Helps build skeleton; buffers pH

- Trace Element: Helps facilitate enzymatic and photosynthetic reactions

- Plankton Suspension: Provides nutrients that are not produced by the target organism

- Vitamin: Helps maintain health, color, and facilitates biological reactions

Marine Aquarium Containing: Crustaceans and other Motile Invertebrates

- Calcium: Helps build skeleton

- Magnesium: Helps prevent premature calcium precipitation

- Iodine: A component of the animal's exoskeleton; aids in the molting process

- Buffer (Alkalinity): Buffers pH

- Trace Element: Helps facilitate enzymatic reactions

- Vitamin: Helps maintain health, color, and facilitates biological reactions

Marine Aquarium Containing: Fish-Only

- Iodine: Helps prevent health disorders such as goiter

- Buffer (Alkalinity): Buffers pH

- Trace Element: Helps facilitate enzymatic reactions

- Vitamin: Helps maintain health, color, and facilitates biological reactions

Replenishing trace elements

Over the course of time, many of the "trace" elements in reef aquarium water become depleted. Several processes are responsible for this depletion. Protein skimming can trap some trace elements with the removed organics and protein. The use of Granulated Activated Carbon (G.A.C.) or other chemical media adsorbs or absorbs some trace elements. Materials of the reef system, like hosing, glass, etc., also adsorb and remove some trace elements. Most importantly, growth of the reef inhabitants reduces the available supply of trace elements.

You can replenishment depleted trace elements in several ways: through feeding, water changes, and liquid supplements.

Whenever you feed your reef, some trace elements are contained in the foods and are used by the creatures digesting the foods. In most reef systems, feeding is done very sparingly to avoid a build-up of waste products. Some hobbyists take this to the extreme and end up with anorexic fish. Please be sure to provide enough food for the proper health of your fish. (Nitrate build-up can be controlled with any number of easy-to-use products.)

All quality salt mixes include the trace elements required by corals, fish, and invertebrates. Monthly water changes of 20 percent to 30 percent are recommended to replenish any elements which may have been exhausted.

In a heavily-stocked reef aquarium, elements are often depleted at a much faster rate, and should be replenished by using commercially available reef supplements. It is best to use the appropriate test kits to monitor the levels of these important trace elements.

Calcium requirements and supplementation

Possibly the most important trace element to be kept at proper levels is calcium, which should ideally be maintained at 350 to 450 PPM. While these levels are far from "trace" levels, depletion of this element is rapid; constant monitoring is required to maintain proper levels. Proper levels of calcium help maintain the carbonate pH buffer system and cause excess phosphate to precipitate, while providing a necessary element for coral skeletal growth.

Calcium requirements and supplementation (continued)

There are several options to replenish the calcium. The most popular method involves dosing the reef aquarium every day with a mixture of lime water (Kalkwasser). Caution must be used to add the Kalkwasser slowly, as a sudden increase can cause a precipitation of magnesium carbonate and can also deplete the pH buffering system, allowing a sudden increase in pH.

A second method to supply the correct level of calcium is to use calcium chloride and a buffer. This method is simple, but it is difficult to stabilize the calcium and buffer levels and can result in unacceptable fluctuations. Tanks with only small amounts of coralline algae and a small population of soft corals could be adequately maintained by this method.

Balanced supplements are available and are easy to use once appropriate levels of calcium and alkalinity have been acheived. These supplements are more expensive and may be cost prohibitive for large tanks with SPS corals.

The last method available to dose calcium involves the use of a calcium reactor with CO2 injection. These reactors are filled with calcium carbonate; a circulation pump within the reactor mixes the saltwater and CO2 to produce a pH of approximately 6.5, allowing the calcium to dissolve into the saltwater. The rate of water discharged from the reactor is several drops per minute and can be controlled by a valve. These systems can be automated with a pH controller and magnetic valve, allowing you to leave the system alone for several weeks, while you take a much needed vacation. These units require close monitoring and the initial cost of the reactor and CO2 system is comparatively high.

Liquid supplements to maintain other trace elements

Addition of the remaining trace elements is best accomplished with the use of liquid supplements. Trace elements can be overdosed into the aquarium, so be careful and monitor these levels with the appropriate test kit and keep and eye on the overall health of the aquarium.

Usually, iodine/iodide is offered by itself, and is important for increased soft coral growth and carapace production in shrimp and crabs. Iodine is depleted by protein skimming and should be kept at 0.06 PPM, although being careful not to overdose.

Strontium is utilized by both hard corals and invertebrates and should be maintained at a level of 8 ppm with the use of a liquid supplement.

Barium (used in coral skeleton growth) and iron (required by the photosynthetic zooxanthellae and macroalgae), are usually available in a trace element supplement. Several of these products are available, and, of course, everyone has their favorites. It is probably best to try several to see which family of supplements gives you the best results. Many reef keepers advocate the addition of molybdenum, though any improvement is the result of improved bacterial (nitrifying and denitrifying) action versus any direct effect on the corals.

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