Abstract: Activator for fluidizing slow-moving material in fluid containers (10). The activator comprises a flat activator hose (15) which is suspended on a support member (16) arranged like a coat-hanger, a conduit (17) projecting into the activator hose between the layers thereof for the supply of pressurized gas pulses to the space between the front and rear layers of the activator hose. At least the front layer of the activator hose is gas-permeable and allows transmission of the pressurized gas pulses to the material in the container, a rhythmical movement simultaneously being imparted to the front layer in relation to the rear layer in pace with the pressurized gas pulses.