I recently bought a small aquarium air pump, not really realizing that “pump” in this case meant blowing air, not sucking. A quick search turned up almost no information online, but converting it into a vacuum pump turned out to be quite easy.
Why might you need a vacuum pump? I’m using it for picking up swarf while cutting vinyl records, but this would also be useful for getting rid of bubbles in mold-making or casting!
I’m using this pump which I got for $13 on Amazon. It’s very small and fairly quiet. To convert it to a vacuum pump, remove the four screws on the back. Inside is a small transformer and two arms. These arms have a magnet at each end, which is pulled by the transformer to activate their rubber bellows. Fortunately, to switch the pump, we just have to reverse the air inlet/outlets: suck air in, push air out vs suck air out, push air out.
Pry up the plastic bellows assembly with a small screwdriver, like shown above.
The inlet/outlet are above, sealed with a rubber O-ring. Pull the assembly out carefully and spin it 90º. Then just push it back into place. Be careful that the O-rings are seated properly, as they seem to want to pop out.
Close up the pump! You may need to seal it using caulk or hot glue if you’re not getting good suction, but mine seemed pretty good without.
Finally, attach the tubes. For more suction, the two tubes can be combined using a T-connector (my pump came with one).
Nothing earth-shattering, but hopefully this helps someone with a similar need!