This work investigated the phytoremediation of mercury (Hg) that is discharged in water by gold mining, using Eichhornia crassipes and Lemna minor. The trials used different initial concentrations of Hg in aqueous solution (0.5, 2.5, and 5.0 mg L-1) over two, four, and six days; at the end of each test, the Hg concentration and pH were analyzed. E. crassipes presented the best performance because they reduced Hg between 97-99% and had low mortality rates between 0-62%. As an aspect to highlight, the adaptation and previous nutrition of the species before their contact with Hg showed significant differences with respect to other studies that used the same species but without adaptation and nutrition. The use of both species for the phytoremediation of Hg yields good results, and E. crassipes was better for its lower mortality values.