[The pollution of water by fish feeding]

Fish feeding causes water pollution by uneaten feeds, by faeces and by excretions via gills and kidneys. Pellet stability is essential for maximizing the consumed proportion of diets offered. At given water temperatures and feeding to satiation feed intake of trout its negatively correlated to dietary concentration of digestible energy. Increasing DE from 15 to 20 MJ per kg reduces feed conversion ratio from 1.33 to 1.00 and, concurrently, reduces the amount of organic matter voided in faeces from 680 to 230 g per kg weight gain of trout. For minimizing water pollution, trout diets containing 20 MJ DE per kg should not exceed 40% Protein and 0.6% P.