If you turn the heaters off you will have a lot of die-off in the sandbed which will render it useless. As a QT you really do not want any sand in the tank.The death knell is getting louder for the nano. The last two fish were removed today. All of the corals have been removed. A few bits of rock yet that I can't fit in the 4x2x2 are still left.
I'd like to sift through the sand looking for worms and the like that I can move over before I finally shut down completely. Part of me is debating turning off the light and heater once I've done that, and just leaving a couple of small power heads running. I really don't want to be doing water changes on this tank every week when it's empty, but theres that part of me that thinks I'd like it to be in a state where I can change some water, turn the heater and lights on, and have it operational enough to be a quarantine tank.
Today is 2 days short of the 1st anniversary of this tank......
If you don't want to keep it running, I would remove everything and give it a good clean out. Then, if you want to use it is a QT do a water change on the DT and use some of this water to fill the QT. Perhaps have a piece of LR in the sump to move over. Use some pieces of PVC pipe as a hiding place for the fish.