An arrangement for introducing gas bubbles into a liquid, a device for fastening a perforated aeration membrane to an aerator base plate, and an aerator base plate therefor. The aerator base plate has an undercut groove in at least one rim region thereof, into which a locking body clamping the membrane in the groove fits clampingly. The locking body has a generally circular cross-section. The groove has an at least substantially oval cross-section. The locking body is designed to be generally cylindrical.