venturi driven protein skimmers inject small air bubbles into the skimmer chamber through the venture valve... the venturi skimmers need correctly sizes pumps that can deal with back pressure and the pumps needs to be powerful enough to make the skimmer run at maximum efficiency... as it was explain to me, the height is needed for more dwell time and why you normally see them super tall, is it better or worse IDK but you read a lot of high parse from the ppl that own lifereef skimmers (not knocking the skimmer in anyway)...
...needle wheel protein skimmers are just modified venturi skimmers with a "needle wheel" impeller. A venturi valve is still used to inject the air, the difference is that the water is drawn through the needle wheel impeller, which chops the incoming air into a super fine mist of bubbles... needle-wheel impellers can reportedly really hack bubbles apart, which is great since small bubbles are ideal for efficient skimming... needle-wheel skimmers are notorious for building a dense, milky froth. This makes for very efficient skimming in a relatively compact package... so requires less height as the super fine mist (foam fractionation) has better contact with the smaller particulars...
