Abstract: An air system analyzer device comprising a flowmeter having a plurality of selectable output ports of respective diameters and a plurality of float members selectively mountable within the flowmeter, together with a method for calibrating the output of a low volume pump and the efficiency of air delivery by the pump through an air system supplied by the pump.

Abstract: An aquarium filter (10) is provided for filtering aquarium water and returning to the aquarium (16) a mixture of air and water. Water is taken from the aquarium by a demand flow syphon system (24) in which water flows into the aquarium filter of the invention as needed. The water is then forced to flow through filtering media, supported on a platform (38) and maintained in compartments (44, 46). The filtered water is introduced to the bottom (80) of a discharge tube (60) which includes a source of air (70). The air is used to pump the filtered water back to the aquarium. Prior to discharge into the aquarium, noise suppression means (94, 96) reduce the noise level of the air/water mixture. The aquarium filter of the invention is capable of operating at flow rates of 50 gal/hr and greater.