Barium

Barium has similar chemical properties to calcium and is also incorporated in coral skeletons as witherite during the precipitation process (occlusion). The species-specific barium-calcium ratio in the skeleton increases with increasing barium concentration and decreasing temperature. The ratio of different barium isotopes in the coral skeleton gives an indication of the salinity at which the coral grew.

Biological relevance: dissolved barium is basically toxic relatively low concentrations and is not essential (necessary for life) according to current knowledge. Barium precipitates very quickly to insoluble compounds and thus loses its toxicity. It is not known whether there are redissolution processes in the substrate or reef rock of marine aquariums and thus the bioavailability increases again.

Barium can be introduced into the aquarium through tap water, food, salt mixtures, aquarium cement or through activated carbon and zeolite. - Barium in drinking water causes reverse osmosis membranes to block extremely quickly and should be made harmless by a suitable pre-filter.

The easiest and safest way to reduce too high barium concentrations is to perform a water change. Adsorbers act too unspecifically.

Natural seawater concentration: 2-93 µg/l
Recommendation for seawater aquariums: 10...100 µg/l
ICP measurements do not distinguish between dissolved (toxic) and undissolved (non-toxic) barium.