Know the difference between a pool and a spa- The main differences between the two are water temperature and amount of water. This is important because higher water temperatures mean more chemical consumption. A spa also holds much less water than a pool does. A pool should be drained every 2-7 years and a spa should be drained every few months (depending on bather load).
Bromine vs chlorine- There is no right or wrong answer here. Bromine is more resistant to heat than chlorine but chlorine can be stabilized (protected against UV rays) while bromine can't be. Whichever sanitizer you chose, I would recommend using a Nature 2 spa purifier. This will allow you to reduce your chlorine/bromine levels to 0.5 ppm.
Water testing- In a spa, I would recommend testing the water 2-3 times a week. This will help you stay one step ahead of any water chemistry problems. The water chemistry in a spa is very similar to a pool.
CLICK HERE TO LEARN MORE ABOUT CHEMICALS How To Maintain A Swimming Pool Part 1 (Chemicals)