Wow..free huh...very nice!!
I'm guessing you're not planning on moving all of the water. That's fine and it would be more like a
water change. As for making the water, all you really need is some
RO water, salt and a power head to move the water around to get it mixed. And yes it does take about 24 hours until it's ready. The other option would be run to your nearest
LFS and buy some from them. I would think with you being in Hawaii, you should have lots of options there.
Now what I'm thinking what I would do if I was in your situation....you have a great opportunity to clean up the tank. Take some
SW and use that to clean the filters. Or just get new ones if it's a type that supposed to be replaced periodically. Throw away the mucked up water if you clean it. Take a scraper to the glass and get rid of all the built up coraline and any other algae sticking to the glass. Scrub off any algae sticking to the rocks, again in SW, not
FW.
Cleaning up everything shouldn't take more than a couple of hours and the fish and such will be fine during that period. Now you add the new water,
LR and get the water up to a proper temp. Around 75-78F or so would be good. Now you add the fish and their water. Get the tank full and start up the pumps.
Also I would transport the fish in bags if you could. Just be sure to have a good amount of air sealed in the bags. And try to make sure you have at least 50% of the original SW from before the move.
Others may have more suggestions.