Importance of nickel as a nutrient in aquaponic systems - some theoretical considerations

This Note paper calls the attention to the important role the microelement nickel plays is the decomposition of urea in aquaponic systems. Since fish feeds do not contain nickel (it is not included in the list of micronutrients essential to fish growth and development) trace amounts of its soluble salts or complexes need to be added to aquaponic systems in order to achieve the systems' stable operation.