Hi, I need to this also and my plan is to put the water in a container, keeping the filter running ( 70ltre storage box or laundry tub ) throw in the heater from old tank. Remove wood and weeds then catch the fish and transfer over. Do the move over to new tank by transferring back over some water plus new treated water at the right temp ,heater, filter then add the fish back. This should result in no temps, filter issues and will in Essence will be a water change. Then decor can be done at my leasure. Even if I just throw weeds and logs back into the new tank for now at least algae etc will survive. With abit of forplanning I can't see a reason why it will take no more than hour. If you have a larger container available you could add fresh treated water to it before the move even starts as that will negate topping up new tank later. Good luck.