There are stain and scale products such as LeisureTime Spa Defender that protects your pumps and heater against scale buildup and hardness problems. This is cheap insurance, IMO. Then there are enzyme products that help with body oils, etc. I do not use one now, but have in the past and found them helpful. Both these products are best used as a weekly or biweekly maintenance additive. Clarifiers should be used only when needed. I have never used a pH hold product, but have heard they cause more problems than they solve.