I'm interested in the subject of minerals in water because by necessity I use only remineralized RO, and would like to use the minimum amount to save money and the time it takes to mix the minerals.
Fish have some ability to adapt to shortages, and ambient water has been shown to be an important source of calcium in cichlids...
http://www.ncbi.nlm.nih.gov/pubmed/2413781
RO water (without the DI stage) contains roughly the same amount of Calcium ion as Amazonian water.
btw, your link is to an analysis of sediments, not water chemistry. See this link:
http://www.scielo.br/scielo.php?scri...32009000600018
There is some evidence that iron can be taken from the water.
"Waterborne iron accumulation by the gills of the zebrafish Danio rerio was assessed...
...demonstrating that uptake of iron from the water is potentially an important source of this nutritive metal in freshwater teleost fish."
http://www.ncbi.nlm.nih.gov/pubmed/12939383/