[Mineral requirements of the rainbow trout (Salmo gairdneri R.)]

Diets of varying mineral contents were fed to rainbow trout weighing about 7 g each initially. During 100 days of the trial good growth rates and food conversion ratios could be observed, when diets contained only 2.0 g CA, 3.4 g P, 0.3 g Mg, 1.6 g K and 2.2 g Na. Remarkable amounts of Ca, Mg and K must have been observed from the water, as retentions of these elements exceeded the amounts fed. With increasing supply of P retentions of P, Ca and Mg increased. Utilization of P from Na2HPO4 was superior to that from ash of fish meal.