An enrichment system using combined organic substrates and carbon sources enhanced cladoceran population growth and nutritional profiles

Cladocerans are widely recognized as one of the most suitable live feeds for the larval and post-larval stages of freshwater fish and crustaceans because of their appropriate size, digestibility, and nutritional value. This study evaluated the effects of fermented carbon sources and their integration with organic substrates on the population growth, nutritional composition, selected polyunsaturated fatty acids (PUFAs), bacterial abundance, and water quality of freshwater cladocerans. In Experiment 1, three cladoceran species, Moina macrocopa (MM), Ceriodaphnia cornuta (CC), and Chydorus sp. (CS), were cultured using five fermented carbon sources: maize starch (MS), rice bran (RB), soybean powder (SB), molasses (MO), and baker's yeast (Y). The most effective carbon source identified in Experiment 1 was subsequently combined with bamboo (MS-BB), paddy straw (MS-PS), and coconut coir (MS-CO) to develop an improved substrate-based culture system for M. macrocopa . Among the carbon source treatments, MM-MS produced the highest population density (46.56 ± 2.00 ind. mL⁻¹), extractable (soluble) protein (81.58 ± 0.84 mg g⁻¹ dry weight), lipid (18.05 ± 0.05%), α-linolenic acid (ALA; 8.81 ± 0.01%), and total quantified PUFAs (22.92 ± 0.15%), while EPA concentrations were among the highest (5.84 ± 0.05%). In Experiment 2, the bamboo substrate combined with maize starch (MS-BB) significantly ( p < 0.05) enhanced the population growth rate and improved the extractable protein (83.09 ± 0.11 mg g⁻¹ dry weight), lipid (19.38 ± 0.04%), EPA (6.23 ± 0.04%), DHA (1.92 ± 0.04%), and total quantified PUFAs (24.60 ± 0.64%) compared with the other substrate treatments. The integrated maize starch–bamboo culture system also maintained favorable water quality conditions throughout the culture period. These findings indicate that combining fermented maize starch with bamboo provides an effective culture strategy for improving the production and nutritional quality of M. macrocopa for freshwater aquaculture.