ok here goes,
i have 2 30gallon recyling containers with dollies on the bootm usually keep both filled one with pure water from the ro di unit one mixed with salt both have 50 watt heaters and hagen 201 powerheads sitting in them then i just use a 1 gallon pitcher to top off the main tank every 3 days , if space allows it this has worked out very well for me it always allows for major water change in case of emergency , and allows me to keep hospital tank empty and clean just fill hospital with main tank water , water change the main unit and your good to go no need to worry about cycle in the hospital