Temperature, Temperature, Temperature! Don't let it drop more than 10 degrees. When I bought my tank, which was set up for a couple of years, I had to move it only 3 miles. Used 32 Gal. trash cans to move the water in 2 trucks. Kept about 150 Gallons. We were pouring the water out of buckets into the trash cans. The temp. outside was about 35 Deg. Took 4 hrs to set the tank back up. Had 3 200 Watt heaters in the water trying to heat it back up and put pots of boiling water in the tank. Didn't help. Lost a 9 inch Clown Trigger, 6 inch Pink Tail, and a 6 inch Stars and stripes. The only fish to make it were the 10 Damsels. The temp. dropped to low 60's plus the stress of the move.
Good thing I got a screaming deal on the tank, helped to offset the pain of the loss.
Good luck.