Organic acids have recently been identified as promising replacements for antibiotics in aquafeeds that promote fish growth and feed efficiency. This study evaluated the inclusion of fumaric acid (FA; 0, 5, 10, 15, 20, and 30 g/kg) in diets (350 g/kg CP; 3.4 kcal digestible energy/g) of Nile tilapia juveniles. Fish (average weight 1.7 ± 0.1 g) were distributed in three 40 L aquaria per treatment (13 fish/aquaria) in a completely randomized design. Over 35 days, the fish received the experimental diets three times daily to apparent satiety. The maximum weight gain, feed efficiency ratio, and protein efficiency ratio were recorded in fish supplemented with 14–15 g/kg FA. After 28 days, Enterobacteriaceae was registered only in the gut of tilapia without FA augmentation. Gram-negative bacteria in the fish gut decreased (p < 0.05) in fish receiving 17 g/kg of dietary FA, increased after this level. The intestinal villi height and width were affected (p < 0.05) by FA levels and feeding time. Thus, inclusion of 15 g/kg of FA was effective in promoting growth, improving intestinal morphometry, and decreasing negative gut bacteria of Nile tilapia juveniles after 35 days.

The aquaculture industry requires green solutions to solve several environmental challenges, including adequate wastewater remediation and natural drug applications to treat bacteria- and virus-related diseases. This study investigated the feasibility of cultivating the dinoflagellate Durusdinium glynnii in aquaculture wastewater from shrimp rearing in a synbiotic system (AWW-SS), with different dilutions of f/2 medium (FM). Interestingly, D. glynnii demonstrated enhanced growth in all AWW–SS treatments compared to the control (FM). The highest growth rates were achieved at AWW-SS:FM dilutions of 75:25 and 50:50. The removal of total nitrogen and total phosphorus reached 50.1 and 71.7%, respectively, of the crude AWW–SS. Biomass extracts of D. glynnii grown with AWW–SS were able to inhibit the growth of the bacteria Vibrio parahaemolyticus (inhibition zone of 10.0 ± 1.7 mm) and V. vulnificus (inhibition zone of 11.7 ± 1.5 mm). The presented results demonstrate that the dinoflagellate D. glynnii is a potential candidate for the development of circularity for sustainable aquaculture production, particularly by producing anti–Vibrio compounds at a near-zero cost.

The present study investigated how dietary inclusion of solubilized mannan oligosaccharide (MOS) influences growth performance, digestive health, stress resilience, and production profitability in Pacific white shrimp (Penaeus vannamei) reared under intensive synbiotic conditions. Juveniles averaging 3.00 ± 0.04 g were stocked at 100 shrimp m⁻² and fed experimental diets containing 0 (control), 1.0, 2.0, or 4.0 g kg⁻¹ MOS for 60 days. Shrimp receiving 1.0 g kg⁻¹ MOS showed higher growth rate, improved feed conversion, and greater final body weight than the control (p < 0.05), indicating enhanced feed utilization efficiency and better overall performance. Gut morphology improved in MOS-fed treatments, with increased mucosal fold height and enterocyte height, suggesting increased nutrient absorption and improved gut functionality. Gut presumptive total count remained relatively stable among treatments, although Bacillus counts tended to increase with solubilized MOS supplementation. Under ammonia and nitrite stress, supplemented groups showed higher survival and reduced gill damage, indicating improved physiological tolerance and health status. Economic analysis demonstrated that 1.0 and 2.0 g kg⁻¹ MOS achieved the best cost–benefit ratios under intensive conditions. Overall, moderate MOS supplementation enhanced growth, gut morphology, stress resistance, and economic efficiency. Polynomial regression analysis, based on the four dietary inclusion levels evaluated, suggested that approximately 1.5 g kg⁻¹ MOS may represent an estimated optimal inclusion level.

This study aimed to evaluate the effect of different forms of artificially salinized on the zootechnical performance, TCBS and Sabouraud Dextrose counts in Penaeus vannamei juveniles reared in a synbiotic system. Four treatments were established in triplicate using a completely randomized design: SD (diluted seawater); LCSM (low-cost salt mix with freshwater); CS (commercial salt); and SW (seawater) in experimental tanks of 60 L, with a density of 2,000 PL m^− 3 for 40 days. An ammonia stress test was performed at the end of the culture and TCBS and Sabouraud Dextrose counts in gut was performed at the 20th and 40th. The synbiotic system proved to be effective in the control of nitrogen compounds. The values of calcium, magnesium and total hardness remained above 30, 75 and 400 mg L^− 1, respectively in low salinity treatments. Better values of final average weight were obtained with the different forms of artificially salinized (LCSM, SD and CS), but survival was lower when compared to SW. There was no influence of different forms of artificially salinized on bacterial counts of TCBS and Sabouraud Dextrose, and on resistance to ammonia stress. Based on the results obtained, it can be concluded that it is possible to rear P. vannamei juveniles in artificially salinized water of low salinity (3 g L^− 1) in a synbiotic system.