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Aims: The present study investigated the effects of different levels using of mealworm (Tenebrio molitor L., TM) on the growth and feed performance, body composition and digestive enzymes of rainbow trout, Oncorhynchus mykiss.
Materials & Methods: Fish (8.58± 0.27 g) in a completely randomized design in 4 treatments and each with 3 replications. Rainbow trout with different levels of 0, 15, 30 and 60% diet (TM0, TM15, TM30 and TM60) (including 50% moisture) of live worm for 30 days. Data were analyzed by one-way (SPSS 17). When p values were significant (P<0.05), means were compared using Duncan's multiple-range test.
Findings: At the end of the experimental, there were significant difference between treatments in growth performance and feed utilization. The results revealed that fish growth parameters and efficiency of nutrient utilization tended to increase with increasing dietary TM levels from 0 to 60%. Feed Conversion Ratio (FCR) was significantly reduced in fish fed the diet with the highest worm level (TM60). The treatments fed TM showed highest protein and lower lipid content compared to fish fed control diet.
The analysis of gastrointestinal enzymes showed that amylase, protease and lipase had a statistically significant difference between the control and other treatments. Protease and amylase activities were found to be significantly higher for fish fed the TM60 diet compared with fish fed TM0 diet.
Conclusion: The results showed that using 60% (TM60) of worm instead of the base diet can improve growth, carcass composition and digestive enzymes.

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 Biofloc technology is considered as a culture system for fish production reduced environmental impacts. In the present study investigated the impact of zeolite nanoparticle on water quality, growth performance, digestive enzymes and immune response of common carp (Cyprinus carpio) reared under biofloc conditions. Fish fingerlings (initial weight of 7.99 ± 0.36 g) were divided into four treatments and fed four levels of zeolite nanoparticles in the following 0 (control), 50, 100 and 200  mg kg⁻¹ diet in biofloc system (NZ1, NZ2 and NZ3) for 60 days. Carbon to nitrogen ratio (15:1) was provided using sucrose. Water quality parameters such as nitrogen compounds were measured during the test period. At the end of the experiment, the highest growth indices and the lowest feed conversion ratio were obtained in 50 mg kg⁻¹ diet (NZ1). Intestinal protease activities in NZ1 and NZ2 treatments were significantly higher than in the other treatments, and the highest lipase and amylase activity was related to the NZ1 treatment. The 50 and 100 Zeolite diets in biofloc conditions significantly enhanced fish immune system activity. The present study suggests that dietary supplementation with 50 and 100 mg Zeolite nanoparticles in biofloc system significantly increases growth performance, digestive enzyme, and immunological response in common carp in fish culture tanks.

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 This research was conducted to determine the effects of garlic extract as feed supplement on the growth performance, body content, blood indicators and culture water quality of rainbow trout (Oncorhynchus mykiss) under stress ammonia. A total number of 156 fish (Average weight 18.37±1.43g and total length 12.27±0.52cm) were reared in twelve 50-L tanks for 60 days (First period: 50 days of feeding with different levels of garlic extract) and (Second period: 10 days under ammonia stress of 0.024 mg /L). Experimental included adding different levels of extract to base food, 0, 0.5, 1 and 1.5% (control, A1, A2 and A3, respectively). The growth performance was significantly higher in fish fed garlic extract supplementation than control. There was a significant difference in feed conversion ratio between different treatments, so that was obtained the lowest in A2 and the highest in control. Protein, immunoglobulin and cortisol concentrations were significantly affected by different levels of garlic. The end of the experiment period, the fish were kept in a close recirculation system for 24 hours. Water sampling was carried out every 4 hours. Water ammonia increased from 16 to 24 hours of the test. At the end of the experiment (time 24), the highest ammonia was obtained in treatment A3 (0.43). In general, the results showed that the addition of 1 to 1.5% garlic extract improved the growth performance and immune response in rainbow trout, while in the recirculation system, the water quality of the rearing environment was better in the control treatment.