White oat genotypes were subjected to Al stress in hydroponic conditions in order to verify the viability of methods based on minimum nutrient solution (MNS) in comparison to complete nutrient solution (CNS), commonly used in the characterization and selection for Al tolerance in this species. The experimental design was completely randomized blocks with three replicates composed of 10 seedlings each. Six white oat genotypes subjected to different Al levels in minimum (0, 3, 6, and 9 mg $L^{-1}$) and complete (0, 10, 20, and 30 mg $L^{-1}$) solutions were evaluated. In this evaluation, the MNS was efficient in identifying aluminum-tolerant, white oat genotypes under hydroponics. The root growth resumption showed to be the most effective trait in the aluminum-tolerant plant selection. At concentrations equal to or higher than 3 mg Al $L^{-1}$ in minimum and 10 mg Al $L^{-1}$ in complete solution, severe damage caused by the toxic element on root development was verified. The white oat cultivars UFRGS 14, ALBASUL, and BARBARASUL showed aluminum tolerance in the tested conditions.