As the old saying goes, "A spa IS NOT a small pool...."
Hot tubs and spas have their own unique features that make caring for them different from pools. The same TFPC Principles apply - self-testing of your water, daily maintenance and never adding anything to it without knowing what effect it will have or without being able to measure it. So no potions, or magic serums, or minerals, or pixie-dust.
A spa can be maintained either as a bromine sanitized water body or a chlorine sanitized water body. Both are adequate but both have drawbacks. If the spa has an ozonator that functions (and they often fail pretty quickly after purchase) then bromine can be easy to maintain using a bromide bank and bromine tablets in a floater. Testing for bromine is a little less specific because you can only measure total bromine, not bromine and combined bromine separately. Bromine spa chemicals tend to be more expensive. Chlorine is less expensive, especially when using the dichlor-then-bleach method, BUT chlorine can fluctuate more day-to-day and often requires frequent/daily additions to keep the spa chlorinated. All spas have LOTS of aeration and so the TA typically needs to be kept low, and borate use is recommended, in order to keep the pH in range. All spas, new and used, are dirty and filled with gunk from the outset and the spa plumbing should be immediately purged on setup using Ahhsome gel to get rid of biofilms, bacteria and manufacturing greases and oils. Once purged, drained and refilled, the spa can then be sanitized either using bromine or chlorine.
Spas will sometimes need to be shocked occasionally depending on bather load and, in a chlorine spa, the CCs will be detectable and rise over time. Usually they are a good indicator of when it's time to drain and refill but, for a typical spa, refilling is recommended at least 3-4 times per year.
There are plenty of articles on TFP about how to maintain a spa/hot tub and lots of help. As always, stay out of the spa store as much as possible and your wallet will be happy.
