72 is likely not too low. Much of the Parana River basin is not tropical but ranging from subtropical to temperate. Thus seasonally experiencing temps below 70s.
As far as I know, those Geos come from Brazil, from an area where tropical climate is bordering suptropical climate.
Don't want to risk it to get health issues.
I've kept mine in the past at 78-79. Lowest they were in was at 73-74 degrees as I kept them in my garage before insulated the entire room and that was winter.
At the low temps they were active swimming the tank with no change of activeness, in other words just being normal. But then again I didn't let them thrive in that temp long before insulating and heating the garage.