The jewel cichlid, Hemichromis guttatus, a fish native to Africa, was introduced into Cuatrociénegas, Mexico, a natural protected area and has negatively impacted native species. To manage its populations, the Trojan-sex chromosomes technique, a genetic method that skews sex ratios over time by releasing YY (trojan) individuals, was implemented. Screening for sexual genotypes while creating YY individuals is crucial to its success. In the current work, we tested two putative genetic markers for the sexual genotype of jewel cichlids after subjecting them to sex reversal treatments. From 15 to 60 days after hatching (DAH), jewel cichlid larvae were fed diets containing either 17β-estradiol (feminization) or fadrozole (masculinization). Using RT-qPCR, the relative gene expression of cyp19a1a and foxl2 was measured at 15, 30, 45, and 60 DAH. Oral administration of 17β-estradiol resulted in 100% feminization; fadrozole achieved 50% jewel cichlid males. The treatments unaffected the organism's length, weight, or survival. Although cyp19a1a was expressed at 15 DAH, its expression was not found in subsequent sampling periods. At 30 DAH, foxl2 levels in the feminized organisms were lower than in the control group. There were no variations in the foxl2 levels between the masculinization and feminization treatments at 45 DAH. According to endpoint PCR, the expression levels started to decline at 60 DAH. The sex reversal period might be shortened if gene expression patterns are taken into account. Our findings support the use of foxl2 for sexual genotype screening in later stages of the generation of YY males.