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.