Red sea magnesium supplement in a 1kg powder form is more economical than the 500ml bottles and is better value for moneythe powder is concentrated so 1g in 100 litres would dose 134ppm of magnesiumrobust coral skeletons are essential for all reefs and only acheivable by ensuring the basic elements calcium magnesium strontium and carbonate are readily available and in the correct ratio to each otherif they are not in the correct ration the coral skeleton can form as a fragile calcite can a