Effect of feeding strategy on tilapia (Oreochromis niloticus) production and water quality in duckweed-based fish aquaculture

52 Fresh and oven-dried (105 °C) duckweed (Lemna gibba) grown on domestic sewage were evaluated as sole feed source for Nile tilapia (Oreochromis niloticus) at a temperature range of 16-25 °C. The investigated daily feeding rates were 25% (dry), 50% (dry), 10% (fresh), 25% (fresh) and 50% (fresh). The feeding rates were calculated based on the fresh weight of duckweed and live body weight of fish. The results showed significantly ( https://www.w3.org/1998/Math/MathML" display="inline"> p < 0 . 05 ) higher SGR for tilapia fed on fresh duckweed than for those of parallel treatments fed on dry duckweed. In case of fresh duckweed, the SGR of tilapia fed on 10% feeding rate had a significantly ( https://www.w3.org/1998/Math/MathML" display="inline"> p < 0 . 05 ) lower value than those fed on 25% and 50%. There was no significant (p >0.05) difference between the SGR of tilapia fed on 25% and 50% for both fresh and dry duckweed. The nitrogen mass balance showed that the highest nitrogen retention was in the treatment with 25% fresh duckweed, resulting in 53% assimilation of duckweed and 28% nitrogen retention from the nitrogen input. Under the experimental conditions applied, 25% fresh duckweed was regarded as the best feeding rate and feed form for tilapia.