Al-n(OH)(m)Cl3n-m and its mixt. with FeCl2 were used as inactivators of P compds. in pot expts. The Ceratophyllum demersum L. (submerged plant), Hydrocharis morsus-ranae L. (floating plant) and Hippuris vulgaris L. (emergent plant) used as test aquatic plants differed in the manner of nutrient uptake in the littoral zone of the aquatic ecosystem. During the 15-week expt., the same doses of Al were added to each vase. After tests, the water pH and Al content in the water and dry matter of plants were detd. Plants were subjected to biometric measurements. Hydrocharis morsusranae L. was the least Al-susceptible plant.