Major & Minor Constituents of Seawater, & Essential Trace Elements

As stated previously, all commercial synthetic mixes are composed of about the same proportions of the major elements of natural seawater (see Table 1 & 2); chloride, sodium, sulfate, magnesium, calcium, potassium, and bicarbonate. Along with bromine, the nine ions that make up 99% of the dissolved salts in natural and synthetic seawater are almost constant.

Seawater also possesses some much smaller concentration of all other naturally occurring elements. Few of these have proven to be absolutely necessary to keeping marine life. Subsequently, artificial saltwater is a simpler medium (See Table 2) than natural, intentionally missing most trace ions. Most of the "trace" materials in ocean water have been found to be superfluous to successful marine aquarium keeping.

A good example is the relative difference between the elements Bromine and Iodine. Bromine is present in the oceans at several thousand times the concentration of Iodine, yet Iodine is far more important biologically. If it becomes limited/absent fishes exhibit goiter-like growths; a common problem in keeping large sharks in captivity.

Major/Minor Constituents:

Complete synthetic salt mixes contain three sets of components; major, minor elements & (essential) trace elements. The minor elements present in most artificial waters are a matter of impurities/contaminants from the other "major" salt ingredients, and for the most part are of little or no biological significance.

Essential trace elements are provided as above with the minor elements and purposely added in one or two phase artificial mixes. All major brands contain adequate amounts of these. There are treatises devoted to the discovered functions of the various major, minor and essential trace elements if you're interested in such. Suffice it here to remind you that standard set-up and maintenance will keep you and your livestock in good stead chemically. The replacement of essential materials for almost all non-reef systems is easily made up by water changes and nutrition.

The exceptions listed previously, intensive aquaculture and reef systems may require or benefit from supplementation. The latter we'll cover in the next section and later under maintenance.

Organic Matters:

To reinforce the virtues of artificial vs. natural water; let's make a brief mention of carbon-based materials.

Natural seawater has a small, but biologically important concentration of organic matter, including vitamins, enzymes, pigments, amino acids, antibiotics and toxins... not to mention the substantial plankton, bacteria, funguses and more from which these largely originate.

These chemicals are best "added" through the processes of proper feeding, and normal healthy metabolism in your system. Just like you and I on the old terra firma, aquatic environments provide essential organics exogenously by way of feeding and endogenously through bio-syntheses.