i just put my fish in buckets, drain the tank water down into some more buckets ( or most of it) so it can be used to refill the tanks once they have been moved. as long as you are using the same filters and mostly original tank water you should be able to add the fish immediately, just check and make sure the water temps are still the same. you can also get away with 50% of the water just treat it like a water change and refill.
I keep no less than 10 buckets in my fish room at all times
You don't need to keep 1 drop of old tank water in the new setup. I've moved tanks around many many times already in my year of keeping fish.
The bucket of old tank water the fish is in doesn't even need to be added to the new/moved tank.
Heres what I do.
Drain tank water into a couple buckets
Put the fish in buckets. Add an air stone if it will take a long while. Possibly a heater.
Toss media in buckets if necessary, otherwise keep HOB/Canister filters full of water.
Drain the tank empty.
Move tank/stand or set up new tank/stand in old tanks place.
Fill up with water and add dechlor. Watching temp of the water that's going in.
Bag the fish in buckets, Ziploc bags work if that's all you have. Float and/or acclimate fish as needed depending on if you know parameters should be the same or not.
Get equipment started up and every thing in place.
Let fish out of bags after temps are roughly the same.
I've moved 2x 55gallon tanks 30 miles or so to my house and set them up without their stand since I couldn't move the stand at the time.
Took down and reset up the 55's again when I got their stand.
Moved 2x 55gallons 1x 10gallon salt and 1x 29gallon into a make shift fish room for a short time.
Moved 2x 55gallons 1x 10gallon salt 1x 29 gallon and 1x 230-260 gallon kiddie pool pond about 5 houses down when I had to move into my grandparents.
Moved 1x 10gallon salt from the basement to the dining room.
Traded up 1x 10gallon salt for a 20 gallon salt tank.
And just recently traded up a 55gallon tank for a 75gallon tank.
