Yes, this will help to remove mineral buildup, but may not prevent it entirely if you have hard water.

Yes, this can be used in combination with other products.

These balls are designed for use with washing machines and dishwashers to reduce the build up of lime scale in clothing and in pipes. While safe for the environment, they are not designed for use with hot tubs or jacuzzis. There is no evidence that they would be harmful in anyway, as they simply soften the water through the use of magnets. However, they were not designed for this purpose.