FROG® Serene Bromine Cartridge | In-Line Spa Systems

The FROG® Serene Bromine In-Line Cartridge is the bromine-releasing cartridge for spas equipped with the FROG Serene In-Line System — FROG's bromine-based water care line, built directly into the spa's filter compartment. It's the consumable that does the daily sanitizing work, releasing a steady, low level of bromine to keep your water clean and clear between water changes. For spa owners who prefer bromine over chlorine, Serene delivers the same "set it and forget it" approach FROG® is known for, applied to a different sanitizer chemistry. The cartridge uses Time Release Bromine Technology — bromine that releases gradually as the water flows through, holding a steady, gentle level instead of the spikes and dips of dosing tabs or granules by hand. Paired with FROG® minerals, the result is cleaner, clearer, softer water using up to 50% less bromine and chlorine than traditional methods. This is the replacement bromine cartridge for the Serene In-Line setup, so keeping one on hand means you're never caught with a spent cartridge and water drifting out of balance. Each cartridge runs about 3–4 weeks depending on use, so most owners go through roughly a dozen of these per year — a strong fit for autoship. Why Time-Released Bromine Matters: Manually adding bromine tabs to a floater or dosing granules creates an inconsistent sanitizer level — too high right after dosing, too low before the next addition. A time-released cartridge holds the bromine level steady, which means cleaner water, less chemistry chasing, and a gentler experience on skin and swimwear. Brand FROG®