The article presents the results of an experimental comparison of the sensitivity of biotests using Daphnia magna Straus, Ceriodaphnia affinis Lilljeborg, Paramecium caudatum Ehrenberg, and Escherichia coli Migula (strain M-17) to water pollution with aluminum compounds. The research was carried out under simulated conditions: the model toxicant was aluminum sulfate Al2(SO4)3∙18H2O, the concentration range per Al was 0.04-2.8 mg/dm3, the pH of the tested waters was close to the neutral level of 7.2-7.8. Bioluminescence of E. coli significantly decreased at an Al concentration of 0.8 mg/dm3 (toxicity index was 93.3±1.2, which refers to a high level of toxicity). The reaction of P. caudatum was weaker: a high level of toxicity was achieved at an Al concentration of 2.8 mg/dm3. These doses did not cause the death of D. magna and C. affinis in short-term experiments (28 and 96 hours, respectively). However, in tests for the chronic toxicity of aluminum, we showed that doses of 0.8 and 2 mg/dm3 Al cause high death of individuals (more than 50%) and a significant decrease in the number of offspring. The range of sensitivity of bioassay methods to water pollution with aluminum turned out to be as follows: bioassay for bioluminescence of E. coli > bioassay for changes in chemotaxis of P. caudatum > bioassay for changes in fertility of D. magna > bioassay for changes in fertility of C affinis.