FROG® Serene Bromine Cartridge (Yellow) | Spa Refill

The FROG® Serene Bromine Cartridge is the consumable yellow cartridge for FROG's bromine-based Serene system — designed for hot tub owners who want the cleaner, gentler water of a mineral-and-bromine program without the daily fussing of traditional bromine dosing. Each 150g cartridge lasts 2 to 4 weeks depending on spa size and use, releasing bromine at the rate you set with the adjustable dial.

This is the standard single-cartridge refill — what you reorder when your current Serene bromine cartridge is depleted. It works in two different setups: the FROG Serene Floating System (a floating dispenser that drifts around your spa), and the FROG In-Line System that comes factory-installed on many hot tub brands. The cartridge is identical for both — what differs is just where the cartridge sits in your spa setup.

The Serene system pairs this yellow bromine cartridge with a separate blue mineral cartridge. Together they sanitize two ways: minerals as a first line of defense against bacteria, plus a low, steady level of bromine handling the rest of the work. That layered approach is what lets the Serene system use up to 50% less bromine than traditional bromine-only programs — gentler water, less smell, and far less wear on swimwear and skin.