In an ink jet printhead have an elongate ink chamber and a nozzle at one end, a continuous flow of ink is provided through a high impedance channel communicating with the chamber close to the nozzle. Ink is ejected through the nozzle by generating longitudinal acoustic waves in the fluid chamber. A high velocity ink flow into the chamber from the channel sweeps away from the nozzle debris or bubbles that might otherwise block the nozzle.