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We evaluated the suitability of fish waste diet (FWD) for culturing the minute rotifer Proales similis through the observation of their population growth and particle size selective feeding. A total of five treatments either with Nannochloropsis oculata or FWD (0.75 and 0.50 g/L) or the combination of N. oculata and FWD were set up in triplicates. P. similis were cultured in diluted natural seawater (8 g/L salinity) and 26 ± 1°C with the diet treatments being applied randomly. We daily monitored the rotifer density, the number of bacteria and the water quality in all the cultures. The population density of P. similis increased exponentially in all treatments, while the mean growth in FWD 0.75 g/L was significantly higher (p < .05) than that in the control. Addition of N. oculata to FWD resulted to lowered P. similis population growth. Bacterial colony count was high in FWD and introduction of P. similis to the diet decreased their density. The estimated bacteria ingestion rates were generally in the range of 6.03 × 102–1.24 × 104 bacteria/rotifer/hr and there was a positive linear relationship between bacterivory and rotifer population growth. We also observed a shift in the particle size distribution with a reduction in the frequency and concentration of small‐sized particles (<2.5 μm) at day 6. These results accentuate the potential of fish‐processing waste as diet for culturing P. similis which feeds on bacteria and small particles (≤2.5 μm) that are by‐products of degradation of this diet.

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Condensed suspension of live microalga cells, for example, Chlorella vulgaris, Nannochloropsis oculata and Tetraselmis tetrathele is often utilized as diets for mass production of live food resources, that is, rotifers, copepods, cladocerans and Artemia. These live food resources are essential for fish larviculture in hatcheries. However, the production of sufficient microalgae is costly, laborious and fragile, and thus require costeffective and stable production technologies, especially for the emerging countries.Studies have shown that locally available biowastes such as fish wastes and chicken manure provide substrates for generating billions of heterotrophic bacterial cells and microparticles as well as growth hormones, which can be used in propagating live food resources. The fish wastes contain essential nutrients that are important for the growth of both live foods and fish larvae. With single feeding of fish wastes, the culture condition of live foods may become unstable, and thus bacterial isolates and selected probiotics, for example, genus Pseudomonas, Moraxella and Micrococcus are needed to stabilize the culture conditions to increase reproduction capacity of the cultured live foods. This article consolidates the results and conclusions of our recent studies on the culture of live food resources, that is, Proales similis de Beauchamp, Brachionus rotundiformis Tschugunoff, Tigriopus japonicus Mori and Diaphanosoma celebensis Stingelin, using waste-generated bacteria from fish waste diet (FWD) and selected probiotics.The non-algal materials reviewed in this article are important to ensure constant supply of cheap live foods to improve aquaculture, especially in the developing countries, which lack sophisticated technology for production of high-density microalgae. K E Y W O R D Sbacterial biomass, chicken manure extract (CME), fish waste diet (FWD), live food, microalgae, single cell proteins (SCP)This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cost of fish production can be reduced by replacement of high-priced fishmeal (FM) with insects sourced ingredients. Four months feed experiment was conducted at a fish farm in Baringo County, Kenya to investigate effects of substituting fishmeal (FM) with black soldier fly larvae meal (BSFLM) on survival and growth performance of C. gariepinus under aquaponic system. Three test diets 35% crude protein content (CP) in which FM was substituted by BSFLM at 25%, 50% and 75% were formulated and experimented with commercial diet of 35% CP. Four weeks old C. gariepinus were stocked in 12 tanks at a density of 50 fish/tank and subjected to the diets. Fish were sampled every three weeks; water parameters were sampled weekly and mortality recorded on occurrence. Diet with 50% BSFLM obtained better FCR for formulated diets with no significance (P<0.05) for FCR and survival. Weight gain of control diet (97.07 g) was significant (P<0.05) compared to formulated diets 64.09g, 69.78g and 67.77g for 75%, 50% and 25% of BSFL replacement respectively. Growth performance and survival demonstrated that BSFLM has potential to substitute FM up to 75%. The fish productivity can be improved and feed cost reduced by incorporating fully defatted BSFLM with CP higher than 25.3% used for the diets.

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