Many Intex pool owners will do their best with the test kit that’s included with their pool until problems arise. Then they take a sample of water to the pool store and then load up the car with whatever the clerk recommends after loading much of their hard earned money into the store’s cash register.
This is not to say that pool stores are disreputable, but keep in mind people with clean pools don’t really need to visit their store and buy their merchandise very often. There is nothing wrong with getting advice from a pool store and purchasing needed chemicals there, but always compare their advice & recommendations with your own knowledge and an understanding of what’s in your water. Also, remember that working at a pool store does not make someone an expert on water quality.