Strontium Chloride 20% Solution Strontium Chloride is a highly soluble form of inorganic strontium which makes it ideal for maintaining dissolved strontium levels in your marine aquarium. Like calcium chloride, strontium chloride has the potential to lower alkalinity levels after prolonged use. ESV's Strontium Chloride Solution is a very pure and concentrated form of strontium, free of phosphates or nitrates.