@Jennifer4287 Unfortunately some guests don't actually read all the info that we provide on our listings, so this might be where the confusion lies.
Your Hot Tub features predominately on your listing, so guests could just think this is what they are getting. The photos are what are going to pull them in, but they might not read about paying extra for the use of it.
I understand setting up as an extra if they would like to use it, but it really shouldn't be in the photos so much, because then the guests "could" automatically think it is included if they don't read the info.
Also I think charging per hour or 2 isn't perfect. Realistically if you are heating up a hot tub, it would just be more sensible/reasonable to charge for the stay not per time limit. Otherwise if they use it longer than that, what are you going to do, request them to vacate the Hot Tub when the time is up ?
Hope this helps.