There are many different methods for moving that work well, I will give you information on the moving method that has worked best for me when I moved aquariums (small and large) for my aquarium maintenance clients (some short distance, some as far as 800 miles)
*Purchase some sterile Rubbermaid containers or Coleman or similar style ice chests (not cheep "styro" ice chests) as well as buckets for ornaments, gravel, etc.
If Rubbermaid containers are used, I prefer as large as possible such as 32 gallons for tanks over 40 gallons.

*Drain water from the display tank into one of these containers. Do not fill more than you can move or will spill. Then add your fish to this water.

*Add Methylene Blue , this will aid in the oxygen capacity of the blood, ease stress, ease ammonia/nitrite poisoning and help prevent disease. I also added Wonder Shells as these would increase the bio load capacity of the water and add very important electrolytes. Keep this container as dark as possible.

Another alternative (not what I generally do, but many prefer) is to bag all your fish adding oxygen or the newer breathing bags. You can also add Bag Buddies by Jungle to these bags. These will add oxygen and Methylene blue for stress and disease prevention. This is a perfectly good method, I just prefer to be able to monitor and even aerate my fish, I also have arrived with less stressed fish this way (including with the breathable bags), as in my opinion the fish feel more comfortable in a larger container with less ammonia buildup and more cover.


*For trips over 4 hours, a battery air pump or AC air pump plugged into an inverter that runs off the vehicles cigarette lighter.
My recommendation here is to use the Azoo Non Stop Air pump (pictured) as this VERY powerful pump (more powerful than many stadard AC pumps) can run up to 20 hours and can also be used as an automatic emergency air pump during power failures or simply as your aquariums main air supply pump.

*Do not over rinse any gravel or bio filter media such as sponges; place these in an open container/bucket

*Place safe (not heavy) decorations in with fish to provide cover. For live plants keep them separately as you will deplete oxygen in the darker moving environment. The same for rocks and heavy decoration as these can injure the fish

*Discard any unused water. For marine tanks I try and save as much water as possible.

*For small tanks (usually under 40 gallons), I will generally leave some gravel and other equipment in the tank for quick moving. For larger tanks I remove everything.

*Once at the destination, I begin to re set up the aquarium. For marine tanks I immediately start up a container with an air stone, water (preferably RO) and salt mix so as to have mixed saltwater ready for use. I will also note that I prefer 24 hours of agitation of newly mixed saltwater before using, however this time is usually not an
option when moving.

*Once the tank is set up and running, I start SLOWLY mixing water back and forth between the tank and fish container to prevent osmotic shock, and adjust temperature.
I will usually add Stress Coat or similar to the container holding the fish and Prime to the display tank just before addition of the fish (and other aquatic creatures)

Summary;
This is not the one and only method to move aquariums (and the inhabitants), but this way and variation of this method have worked very well for me with almost no losses over dozens of moves for my clients.