A fluid transfer device for transferring fluid into or out of a fluid vessel, such as a tank, and is particularly useful in transferring fluids with particulates or high viscosity in a substantially aseptic, hygienic, or sterile manner. The device has a body with an elongate passage extending through the body. The body has a proximal end and a distal end. A longitudinally displaceable shaft is disposed in and extends along the passage in the body. A plug sealing the passage is at a first location. A diaphragm sealing the passage is at a second location intermediate the plug and the distal end of the passage. The shaft extends through and is secured to the diaphragm. A fluid transfer opening is located in the passage between the diaphragm and the plug. Longitudinal displacement of the shaft causes the fluid transfer opening to be in fluid communication with a fluid vessel, the diaphragm stretching to accommodate the displacement of the shaft while maintaining an aseptic seal of the passage.