While using bromine to clean your hot tub can be a good alternative to chlorine, it is still a pretty harsh chemical that can irritate your skin and eyes with use. There are other things you can try if you want a clean hot tub without all the nasty chemicals.
Using white vinegar and water can help break up calcium deposits and it is easily rinsed away. For those that worry about bacteria build ups you can buy some natural enzyme tablets to drop in your tub, which will make short work of the germs.
Another classic cleaning method is to use baking soda paste to give your hot tub a good scrub. You'll be shocked at how clean your tub can get without using things like bromine and chlorine.