Had to do the same thing from the old 55 to the new 90. I moved all the rock to the bottom and drained the water into 5 gallon bottles down to about 6 inches. Then me and a neighbor liftet the tank and metal stand and hauled it into the kitchen to it's temporary resting place. Filled it back up and then started up the new tank. Once it was ready I moved stuff over piece by piece.. Here is the new one: