Sea-Lab Formula 28 is a mixture of naturally occurring buffer compounds that maintains natural ocean concentrations of calcium, strontium, and all 15 essential trace elements. Calcium and strontium are well recognized nutrients, but trace elements are not as well understood. They are, however, vitally necessary to marine life in the aquarium. Paradoxically, these same elements, so essential to life, are also highly toxic. The trick is to tread the fine line between trace element starvation and trace element toxicity. Formula 28 is the first formula available to hobbyist and professionals that creates and maintains this fine balance. As elements are depleted from solution, Formula 28 delivers exactly equivalent amounts to replace them.