Strontium

Strontium has similar chemical properties to calcium and is therefore incorporated together in bones and coral skeletons as strontianite. Similar to barium, the species-specific strontium-calcium ratio in coral skeletons increases with decreasing temperature.

Biological relevance: Strontium is incorporated into calcium structures (bones, skeletons, statocysts) by many organisms. Whether strontium is essential (necessary for life) or incorporated accidentally or intentionally for detoxification is not certain. Studies show that strontium uptake is also dependent on the concentration in the surrounding water and the rate of calcification of the coral. - It is certain that strontium is found in different group of organisms: Radiolaria and Acantharia, some snail, Cephalopoda, calcareous red algae. - High radiolarian concentrations may lower strontium concentrations in seawater.

Because increased strontium additions can accelerate SPS growth, it was hailed as a "miracle cure" in early SPS aquaristics and sometimes used excessively without a reliable determination of strontium concentration. - The presence of strontium is thought to accelerate calcium uptake. Strontium is far less toxic than, for example, barium. However, some organisms are said to be sensitive to unnaturally high concentrations.

Strontium can be introduced into the aquarium by tap water, salt mixtures and calcium preparations (e.g. lime material for calclium reactors). - Strontium in higher concentrations in drinking water causes reverse osmosis membranes to block extremely quickly and should be rendered harmless by a suitable pre-filter.

The easiest and safest way to reduce too high strontium concentrations is to make water change. Adsorbers act too unspecifically. If the source of the strontium is known, it should be reduced.

Natural seawater concentration: 8...80 mg/l
Recommendation for seawater aquariums: 8...10 mg/l