I used to use vinegar, but it takes quite some time, like you guys say, an overnight soak. But after speaking with another reefer, he told me he uses muriatic (hydrochloric) acid, which takes only a minute or 2. Initially, I was a bit concerned since HCl is a powerful acid, but he assured me that the plastics and metals the pumps are composed of are not affected by the acid. I think muriatic is diluted to a 20% soluition (don't aske me what molar that is... I slept through chemistry) and I further dilute it another 300-400%. But be careful of the fumes, you'll want to be outdoors or in a well ventilated area!!