**ABSTRACT **

This study aims to determine the effect of the level of use of fermented coconut testa from Rhizopus oryzae for four days on optimal artificial feed on the growth of red tilapia fry. The method used in this research is an experimental method using a completely randomized design (CRD), which consists of five treatments and three replications. The treatments used were differences in the level of use of fermented coconut testa in feed (A) 0%, (B) 5%, (C) 10%, (D) 15%, and (E) 20%. Maintenance was carried out for 42 days. Parameters observed were nutritional value of fermented products, daily growth rate, feed conversion ratio, and water quality (temperature, pH and dissolved oxygen). Daily growth rate, feed conversion ratio, and water quality were observed every 7 days. Daily growth rate and feed conversion ratio data were analyzed using the Analysis of Variance (ANOVA) with a 95% confidence level, followed by Duncan’s multiple spacing test, while the nutritional content of fermented products and water quality were analyzed descriptively. The results showed that the use of coconut testa fermented by *R. oryzae* for four days as much as 15% in the feed formulation gave the highest daily growth rate of red tilapia fish, namely 1.29% and feed conversion ratio of 2.36.

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