The drip method is the one preferred by most modern aquarists. It not only allows your fish to get used to the temperature of your tank, but also adjusts them to the pH, hardness, and numerous other water parameters. It is easy to do and only takes about 30 minutes to an two hours depending on the speed of dripping.
As the name implies the drip method of acclimation, or drip acclimation, introduces aquarium water at a controlled rate of mere droplets per second. This precision control greatly minimizes stress on new arrivals. Drip acclimation generally involves a siphon device and a method of regulating aquarium water entering the container housing new arrivals. Aquarium water is introduced at a rate of about 2-4 drips per second. Until the recent past, drip acclimation devices were handmade and employed mostly by experienced reef aquarium hobbyists. However, this "advanced" technique of acclimation can be enjoyed by hobbyist of all levels thanks to the availability of convenient, commercial drip acclimation devices.
(Copy and pasted from websites)
