text: The premise behind these skimmers is that a high pressure pump combined with a venturi, can be used to introduce the bubbles into the water stream.  The tank water is pumped through the venturi, in which fine bubbles are introduced via pressure differential, then enters the skimmer body.  This method was popular due to its compact size and high efficiency for the time but venturi designs are now outdated and surpassed by more efficient needle-wheel designs.