Just new to hot tubbing and checked my water. IT shows no free chlorine. Do i need this if I am using bromine tabs to sanitize my tub ?Cause my bromine levels is good and i have no chlorine tabs to add to get it up to the level needed. Will this harm anything ?My understanding is if you have one you dont neccasarily need the other or am I wrong on this? thanks for any help.

Yes, you are correct - you only need either Chlorine or Bromine. If you ever decide to switch from Bromine to Chlorine, or the other way around, you need to drain/refill the spa - they are not compatible.

Test strips often test for both Bromine and Chlorine to save manufactuers making two different types of test strip.

Sounds like you have some universal test strips that do both, so dont worry; as long as one of the two readings is correct, you are fine.

The two are completely compatible. If for some reason you want to switch from all-chlorine to bromine, just start using bromine tabs and you can continue to use granular or liquid chlorine for shock.

If you want to convert from bromine to chlorine a drain and refill is helpful because the bromine will be hard to get rid of, however you can use all chlorine products without concern.

Bromine tabs are in the range of 70 percent chlorine. Test you pH often if using bromine tabs. They are very acidic.