How to Start Up and Maintain a Hot Tub with the FROG® Serene® Floating System

The FROG Serene Floating System is the green lilypad floater that combines a blue Mineral Cartridge with a yellow Bromine Cartridge. Together they sanitize with up to 50% less bromine than a tablets-only routine, which means softer-feeling water and less bromine odor. This guide covers the full startup and a simple weekly routine.

Bromine system, not chlorine: Serene uses bromine chemistry. It is not interchangeable with the chlorine-based FROG @ease, and the cartridges do not mix between systems.

Serene fits owners who prefer bromine — often because they find it gentler on skin and sinuses, or because it stays effective across a wider pH range than chlorine. The floating version works in any hot tub from 200 to 600 gallons with no installation: snap in two cartridges and let it float. If your spa has a FROG cartridge well built into the shell, use the Serene Inline guide instead — the inline system uses a green bromine cartridge and its own procedure.

• Floating FROG Serene Bromine Bundle — floater, 4 bromine cartridges, 1 mineral cartridge, test strips, 3 Maintain packets, Jump Start (about a 4-month supply for tubs up to 500 gallons).
• FROG Serene Floating Starter Pack — smaller startup option.
• FROG Serene Bromine Cartridge — single replacement; or the Serene Kit (3 bromine + 1 mineral).
• FROG Test Strips (bromine/chlorine) — reads the low bromine levels used with FROG minerals.
• FROG Jump Start — startup shock.
• FROG Maintain — weekly non-chlorine shock.
• FROG Balancing Basics Kit — or individual balancers: Target, JumpH, DropH, SooTHe.
• Hose pre-filter and metal control for the fill.

Before you fill

• Rinse/clean the filters (or install new ones).
• Open all jets, set valves normally, close the drain, check pump unions and drain plugs.
• If the spa sat unused, purge the plumbing with a pipe & jet cleanser before the fresh fill.

Fill the right way

Fill through a hose pre-filter, through the filter compartment when possible. FROG specifically advises treating source water that’s high in iron or other metals with a metal control product — we use Leisure Time Metal Gone. If sanitizer disappears fast later, or the water fights you, test for phosphates and treat with SeaKlear Free & Klear.

FROG Serene target ranges

These are FROG’s published ranges for the Serene Floating System. Alkalinity comes first, even if correcting it throws pH off further. FROG’s Serene instructions say to add balancers in small increments one at a time with the jets on, then wait about 6 hours before retesting and adding more. If hardness is high, partially drain (about 6 inches) and refill with softer water; if low, add a calcium increaser.

1. Establish the initial residual with Jump Start

After balancing and before the floater goes in, establish an initial 1.0–2.0 ppm residual with FROG Jump Start — one packet per 600 gallons. Per FROG’s Serene Floating instructions, do not substitute a non-chlorine shock for this startup step (that’s for weekly maintenance later).

2. Set the cartridges

Set the blue Mineral Cartridge to #6 and leave it there for its whole life. Set the yellow Bromine Cartridge by your spa’s gallons:

Source: FROG Serene Floating System operating instructions setting chart. Your spa’s owner’s manual lists its gallon capacity.

3. Float it

Snap both cartridges into the green floating holder and let it free-float. When you soak, lift the floater out, drain it into the tub, and set it on a bleach-safe surface — and remember to put it back in when you get out.

For the first week, test daily with FROG Test Strips and adjust the bromine cartridge up or down one setting per day until the strip holds in FROG’s ideal range of 1.0–2.0 ppm bromine. That low target is intentional — the minerals carry part of the sanitizing load, which is how Serene runs up to 50% less bromine than a conventional bromine tub. Never let bromine fall below 1.0 ppm.

Weekly “5-minute” routine

• Test water (alkalinity → pH → bromine 1.0–2.0 ppm).
• Adjust only what’s needed, in small steps.
• Shock weekly with FROG Maintain (non-chlorine, single-dose packet) — more often under heavy use. This is FROG’s published cadence for Serene; it oxidizes oils and lotions so the bromine isn’t wasted on them.
• Rinse filters weekly; deep-clean monthly with Leisure Time Filter Clean.
• Wipe the waterline if a ring forms.

Don’t reuse spent cartridges. A 4-month-old mineral cartridge is the most common hidden cause of “my bromine can’t keep up” — without working minerals, the low Serene bromine level isn’t enough on its own.

Cloudy water or low bromine

• Check water balance first — pH and alkalinity must be in range for Serene to work.
• Check the bromine cartridge; replace if empty.
• Check the mineral cartridge’s age — over 4 months means replace it now.
• Shock with FROG Maintain.
• Persistent trouble? Test phosphates (target range on the test: low; high phosphate feeds algae, and algae burns up bromine).

High bromine

Take the floater out of the tub until bromine drops to 2.0 ppm, lower the bromine cartridge setting by one, return the floater, and retest in 24 hours. Repeat until it holds 1.0–2.0 ppm.

Drain and refill on your manufacturer’s schedule or whenever the water becomes hard to manage. Purge the plumbing with a pipe & jet cleanser before draining, use a utility pump to speed the drain on bigger tubs, and install a fresh mineral cartridge with every refill.

FROG Serene Inline System Guide

Same mineral + bromine chemistry, but built into the spa shell with a green bromine cartridge. Use that guide if your spa has the FROG cartridge well.

Traditional Bromine Tablets Guide

Prefer classic brominating tablets in a floating dispenser? Full startup and weekly routine, including the sodium bromide reserve most owners skip.

Browse all guides on the EZ Hot Tub Water Care hub.