Active Oxygen is a tried and tested alternative method of keeping your spa safe and clean without using halogen based sanitisers such as Chlorine or Bromine. Bayrol is really simple to use by introducing 1 cap of Bayroplus liquid per week then adding a Bayroklar tablet 15 minutes before each spa use...it's as simple as that! Bayrol products are compatible with all SpaGuard products. Test for active oxygen content using bayrol test strips.