I'm doing work in microfluidics, and need help selecting a vacuum pump as I have no experience in creating or controlling a vacuum. Let me simplify my device: I have water confined between two plates. One of the plates has a hole, covered with a small patch of material that lets gas through, but not water. I want to remove the gas from the water using a vacuum, with tubing going directly from the patch to the pump. This system is small, at 5 cm x 2 cm x 0.02 cm and therefore delicate. My tubing will be between 1/16" and 1/4" inner diameter. I'm designing my system based on the following quote: "The air trap was first connected to a vacuum source, which was the house vacuum at -97 kPa relative to the atmospheric pressure. Knowing little of gage pressures and so forth, I assume this means that I need to maintain a pressure of 101.3 - 97 = 4.3 kPa? For convenience, this is about 30 Torr, or 30 mmHg. Here is a chart of vacuum pressures I found on PF.com: Atmospheric pressure 760 Torr 101.3 kPa Low vacuum 760 to 25 Torr 100 to 3 kPa Medium vacuum 25 to 1×10-3 Torr 3 kPa to 100 mPa High vacuum 1×10-3 to 1×10-9 Torr 100 mPa to 100 nPa Ultra high vacuum 1×10-9 to 1×10-12 Torr 100 nPa to 100 pPa Extremely high vacuum <1×10-12 Torr <100 pPa This puts me on the border between a low and a medium vacuum. I need something small, inexpensive (< $300, the cheaper the better), and not loud because other people work near me. I want to use a hand operated pump (http://www.crscientific.com/vacuumpumps.html) but it only goes down to 50 mmHg or 50 Torr. Can you please offer some advice? Would a hobby pump work for a fish tank, for example?