Buying an established 90 Gallon tank

[jesscolavt]

Hello,
On Wednesday, I am buying an established 90 gallon tank from someone about 1.5 hours away. I am wondering how much of the tank's water I should be trying to bring with me, at a minimum? There is a convict tang, as well as live rock to transport. My thought was that I would get some 5 gallon buckets, and wondered what the minimum amount of water you would suggest transporting.
Thanks!

 

[jesscolavt]

This is the tank:

 

[florida joe]

Nice tank IMO just bring the water needed to house the fish and corals if any during transfer, take water samples of the tank you are buying and match NEW water as close to those parameters as you can
If the parameters of the purchased tank are not to your liking just dip acclimate the fish to your parameter preference when you set up the tank in your home