I used to use the large, heavy trash containers. I'd get them from the local hardware store. Used them to store the clean, treated water and used another for holding the old water I removed during the water change. A tank heater can be used to keep the new water within a few degrees of what's already in the tank.
Water changes keep pollutants out of the tank. I remove more than most, about 60 percent weekly. I change so much water, I can safely use a much smaller filter. The filter is just moving clean water. Don't have to ever test the water, I know the chemistry is balanced, little or no dissolved wastes.
It's all about the water.
"Fear not my child, just change the tank water."