Growth rate and tissue magnesium concentration in adult freshwater tilapia, Oreochvomis mossambicus (Peters), fed diets differing in magnesium content

The growth rate and magnesium concentration in scales, bone and muscle of freshwater tilapia, Oreochronüs mossambicus (Peters), initially weighing between 70 and 300 g, were followed during low‐magnesium feeding. The growth rate decreased in fish on low‐magnesium diets, but no changes were observed in the magnesium concentration in the scales, bone or muscle. No changes were observed in calcium or sodium concentrations in these tissues. We conclude that adult tilapia fed a low‐magnesium diet manage, in contrast to other fish species, to maintain their magnesium balance and must therefore obtain magnesium from the water.