Effects and economic viability of earthworm meal (Eisenia andrei) and zeolite in diets for Nile tilapia (Oreochromis niloticus) fingerlings

This study evaluated inclusion levels (0, 3.5, 7, and 10.5%) of earthworm meal (Eisenia andrei) in diets for GIFT Nile tilapia (Oreochromis niloticus) fingerlings with and without 2% zeolite. The experiment used a 4 × 2 factorial design with three replicates, involving 24 tanks, each stocked with seven fish (2.672 ± 0.22 g). Water quality parameters, growth performance, proximate composition of fish carcass and biometric indices were analyzed, along with an economic assessment. Results showed that zeolite significantly reduced nitrogenous compounds and coliforms in water (P < 0.05). Earthworm meal did not affect water quality (P > 0.05). However, 7% and 10.5% inclusion of earthworm meal significantly improved growth performance (P < 0.05), including final body weight, weight gain, feed conversion ratio, feed efficiency, specific growth rate, protein efficiency ratio, and condition factor. Zeolite did not affect growth performance (P > 0.05). Proximate composition and biometric indices were not significantly impacted by either product (P > 0.05), except for lower carcass ether extract with zeolite and higher protein and energy retention coefficient with 7% and 10% earthworm meal (P < 0.05). Economically, diets with earthworm meal were more expensive (USD 25.05/kg), but the viable price was determined to be USD 1.27/kg, without negatively affecting economic indices. Zeolite did not significantly impact other economic parameters (P > 0.05). In conclusion, earthworm meals can be added to Nile tilapia diets at 7% to 10.5% to enhance growth performance, with 7% recommended for cost considerations. Zeolite at 2% can improve water quality without affecting production costs.