Supplement containing highly concentrated strontium and barium. Strontium, after calcium and magnesium, is one of the most important elements needed for growth of hard corals. Strontium supports the formation of hard coral skeletal tissue and significantly improves the calcium absorption. It also supports the growth of soft corals. In a closed aquarium system, skimmer and filtration media remove strontium deposits from the water, therefore its supplementation is necessary. In order to ensure that the aquarium conditions are as close as possible to the natural ones, the preparation was enriched with the addition of barium, which is also present and significant in seawater. Thanks to the appropriate proportions, Strontium effectively complements the strontium and barium deficiencies in aquarium water and guarantees the perfect ratio of these elements. The strontium level in the reef aquarium should vary between 5 ppm and 15 ppm.