Sargassum sp. meal is a plant ingredient that has not been used properly, and its potential has not fully realized as an herbivorous fish diet. This experiment aims to determine the potential use of sargassum meal in the grow-out of the rabbitfish diet. Rabbitfish (initial weight of 51.76 ± 0.11 g ind−1) those were cultivated in fifteen floating net cages sized 1×1×1.5 m3 at 20 fish cage−1 stocking density lasted for 90 days. This experiment was designed as Completely Randomized Design with five treatments of sargassum meal dosages in diets, which were 0.0, 7.5, 15.0, 22.5, and 30.0%, with three replications each. The results showed that no significant effect (P>0.05) of different sargassum meal dosages on the specific growth rate and survival rate of rabbitfish. However, feed intake increased with increasing sargassum meal, where the highest was obtained at 22.5% (275.6±9.2 g fish−1) and 30.0% (270.8±8.4 g fish−1) dosages which were significantly higher (P<0.05) than the other dosages. At the same time, sargassum meal dosages were significantly different (P<0.05) on feed efficiency and protein efficiency ratio, where they both seem to decrease with the increase of sargassum meal. The highest feed efficiency was obtained at the dosage of 0.0% (68.6±3.6%) that had no significant effect (P>0.05) with 7.5% (63.7±2.2%) and for protein efficiency ratio was obtained at 0.0% (2.29±0.12) that had no significant effect (P>0.05) with 7.5% (2.20±0.08) and 15.0% (2.12±0.05) dosages. The use of sargassum meal as much as 30.0% caused a lower crude lipid and higher crude protein contents in the nutritional body composition of rabbitfish, and was significantly different (P<0.05) compared to 0.0% dosage. Based on the growth rate of fish, the optimum dosage of sargassum meal in rabbitfish grow-out diet was estimated at 19.46%, but only 7.5% of sargassum meal could be used in the diet based on feed efficiency.

Rabbitfish (Siganus guttatus) is a herbivorous fish that can utilize a plant-based diet better than omnivore and carnivorous fish. However, the quality of the plant-based diet still needs to be improved so that the rabbitfish can grow faster with better feed efficiency. One effort that is thought to be done to improve the quality of diet is fermentation. Therefore, this study aims to evaluate the use of effective commercial microorganisms (EM-4) probiotics in the fermented plant-based diet on the growth performance of rabbitfish. The treatments tested were fermentation of ingredient plant-based diet using EM-4 at different doses namely: F10 (10 mL), F20 (20 mL), F30 (30 mL), F40 (40 mL) per kilogram substrate and WF (unfermented diet). The test diets were given to the rabbitfish juvenile that was cultured in floating net cages in the sea. The initial weight of the test fish is around 48 g, maintained in 15 units of 1x1x1.5 m cage; they fed with satiation in the morning, afternoon, and evening for four months. The results showed that the fermented diet with EM-4 at all doses tends to increase in the content of free fatty acid, total n-3, total n-6, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) compared to these fatty acids contents in the unfermented diet. The specific growth rate, weight gain, feed efficiency, and protein efficiency ratio was not significantly different (P>0.05) between the treatments. Feed intake was significantly different (P<0.05) between treatment, and it was highest in fish fed the unfermented diet compared to fish fed the fermented diet. Fermentation of the test diets with EM-4 has not been able to improve feed utilization and growth of rabbitfish.

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Moulting in crabs can be accelerated by adding moulting hormone. Phytoecdysteroids are an active compound found in certain plants, for example amaranthus, that are analogous to the moulting hormone in crustaceans. The aim of this study was to determine the effect of phytoecdysteroid administration through injection and artificial feed on moulting and growth of mud crabs (Scylla olivacea). Mud crabs with carapace width 61–62 mm and weight 50–51 g were reared in individual crab boxes with dimensions 25×20×20 cm. The selected crabs were injected with amaranthus extract at a dose of 1 mL/crab (I), then placed in the crab boxes and kept in a pond. Amaranthus leaves were dried in an oven at 60°C for 24 hours, ground using a hammer mill, and mixed with other feed ingredients. Different doses of amaranthus flour were applied: 0% (control), 10%. 12.5%, 15%, 17.5% and 20%. Moulting and growth data were analysed for a variance. The results showed that the administration of phytoecdysteroids from amaranthus by injection and through artificial feed had no effect on the percentage of mud crabs moulting, survival rate, growth, and feed conversion value. The mud crabs were not able to take full advantage of the artificial feed provided because of the inappropriate size of the feed and the fragile structure that cause wasted and uneaten feed.

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