The FROG® Serene Cartridge Kit is the multi-pack refill for FROG's bromine-based Serene system — one bromine cartridge and one mineral cartridge, giving you approximately four months of water care supply for a single hot tub. It works with both the FROG Serene Floating System (the dispenser that floats in your spa) and the factory-installed FROG In-Line System built into many hot tubs. The math is straightforward. Each Serene bromine cartridge lasts 2–4 weeks; the mineral cartridge lasts up to 4 months. So one mineral cartridge plus one bromine cartridge is roughly one month of supply for a typical hot tub — perfectly aligned with the mineral cartridge's lifespan. Buying this kit costs significantly less than buying the cartridges individually, which is exactly the point. The chemistry itself is the proven FROG® Serene formula: FROG® minerals plus Time Released Bromine Technology work together to sanitize your water two ways. The minerals condition the water and provide a first line of defense against bacteria, which means the bromine cartridge can run on a low, steady release — typically up to 50% less bromine than a non-mineral bromine program. The result is soft water with much less odor, less wear on swimwear, and no daily spooning of bromine tabs into a floater. Why a Kit Pays Off vs. Buying Separately: Most Serene owners burn through three bromine cartridges before a single mineral cartridge is spent. Buying them together in one kit is significantly cheaper than purchasing four single cartridges over the same four months — and it means you only have to remember to reorder once per quarter instead of every 3–4 weeks. Brand FROG®
