Any ideas how to reduce water volume in the hot tub?

[Nico Kabor]

Hi, Our Jacuzzi J-315 circa 2012 is a 4 person spa, but we only ever use it one person at a time. As such, one half of it is never used. We are wondering if there are ways to fill the unused half with a bag of (something??) so there's less water in the spa, and thus less energy necessary to maintain the temperature.

E.g. we could add an air balloon, but obviously it will float up. Or maybe a bag of rocks but I suspect rocks take just as much energy to maintain temperature as water? Something like a double walled box of rocks (with air in between the walls) would probably do it but that's getting into the crazy territory. Any thoughts?

Thanks,
Nico

[waterbear]

Less water also means more water maintenance, more frequent water changes, and less forgiving if your sanitation routine slips a bit. Bottom line, the larger the volume of water, the easier the water maintenance.