Nutrient budgets in tanks with different stocking densities of hybrid tilapia

Nitrogen and phosphorus budgets were estimated in 12 indoor fiberglass tank s stocked with hybrid tilapia (Oreochromis niloticus x O. aureus) at densit ies of 1 kg, 5 kg, 10 kg and 15 kg/m(3) and reared for 14 days. Each densit y was replicated three times, and the experiment was repeated five times. T he water in each tank was changed daily. Fish were fed a 34% protein tilapi a feed to satiation twice daily. Feed consumption rate significantly decrea sed (P < 0.05) with increasing density, but the FCR did not vary significan tly (P > 0.05) among the treatments. The production of one kilogram of fish required 2.0-2.2 kg of feed in different stocking density treatments, whil e 87.1-95.6 g nitrogen and 12.6-13.8 g phosphorus were released into the wa ter, as metabolic waste. Of the feed input, 21.4% of the nitrogen and 18.8% of the phosphorus were incorporated in the fish harvested. (C) 1999 Elsevi er Science B.V. All rights reserved.