I did a 72 gallon tank. It wasnt hard but took a long time. First I got five rubbermate containers from Walmart. Separated LR, coral, tank water, and fish into different containers and with the help of few friend drove the almost empty tank with only sand left over to the new place. Then another 4 trips back and forth till all the containers were moved. Once the tank has settle in it's new location, I started to refill the previously saved tank water follow by the LR. Mean while I had a power head circulating in each of the coral and fish container just to keep the oxygen level up. I did fill the rest of the tank up with so premade new tank water in the new place and raised the temperature to the proper level, finally the rest of the coral and fish went back in. I have done this a few times, it seems to work good. Never really lost anything from the transport. Now if you want to talk about broken equipment during a move, that is a different story.
If I were you I would do a partial water change when you set up the tank in the new location so you don't need to carry any extra unnecessary weight, make sure extra fresh saltwater is premixed and ready to go just incase of a mishap. Be careful with equipment and make sure you don't use new sand if you don't have to and don't rinse out your tank or any other biological filter material. 20 gallon tank move should be easy breeze.
