The invention relates to methods, compositions and kits for raising marine fish in freshwater. The methods involve adding at least one Polyvalent Cation Sensing Receptor (PVCR) modulator to the freshwater in an amount sufficient to increase expression and/or sensitivity of at least one PVCR; and adding feed for fish consumption to the freshwater, wherein the feed comprises an amount of NaCl sufficient to contribute to a significant increased level of the PVCR modulator in serum of the marine fish.