Hot tub pump

I have a few questions about my recently obtained pre-owned Krevco SSPA-1 Sunrise HOT TUB. About 17 years old, with limited use.
1. Should the circulation pump be running all of the time?
2. Currently there are always air bubbles in the water being circulated. Is this normal? Or does this indicate an air/plumbing leak?

Thanks for taking the time to answer my questions.