Description
Fresh Mineral and Bromine for Your Built-In FROG Serene In-Line Holder
The FROG Serene In-Line Cartridge Refill pairs one blue FROG Serene Mineral Cartridge with one green 200 g FROG Serene In-Line Bromine Cartridge. It is made for hot tubs with a built-in FROG Serene In-Line holder, a system FROG lists for select Marquis, Caldera and Hot Spring models.
Swap both at your next mineral change and the cartridges snap straight into the holder. This refill ships free to US addresses on online orders at HotTubPirate.com.
Matched Cartridges for Built-In Holders
In-line hot tubs hide the FROG holder under a cap in the top of the spa. This refill gives you the two cartridges that holder takes: blue mineral on top and green 200 g bromine below.
The Larger 200 g In-Line Bromine
FROG makes a special 200 g bromine cartridge for the In-Line System. It holds more bromine than the yellow 150 g cartridge. Either size fits the in-line holder or the floater.
Clean Water With Less Bromine
With FROG minerals working alongside the bromine, the system holds 1.0 to 2.0 ppm. FROG says that is up to 50% less bromine than the ANSI minimum, for softer-feeling water.
Key Features and Benefits
- 1 Blue Mineral Cartridge4 months, set to #6.
- 1 Green 200 g Bromine2 to 4 weeks, adjustable 0–6.
- Built-In Holder FitFROG Serene In-Line System.
- Select Marquis, Caldera and Hot SpringPer FROG's In-Line page.
- PrefilledNo measuring or pouring.
- Lower BromineHolds 1.0–2.0 ppm with minerals.
- Free US ShippingOn online orders at HotTubPirate.com.
Product Details
| Product Detail | Information |
|---|---|
| Brand | FROG (King Technology, Inc.) |
| Product | FROG Serene In-Line Cartridge Refill |
| Kit Contents | 1 FROG Serene Mineral Cartridge (blue) and 1 FROG Serene In-Line Bromine Cartridge, 200 g (green) |
| Product Type | Replacement cartridges for the FROG Serene In-Line System |
| Made For | FROG Serene In-Line System, select Marquis, Caldera and Hot Spring hot tubs (dealers also list Artesian) |
| Hot Tub Size | Up to 600 gallons |
| Bromine Cartridge | Green, 200 g (dealers list 7.1 oz), order code 01-14-3829 |
| Water Balance (In-Line Manual) | pH 7.2–7.8, total alkalinity 80–120 ppm, hardness 150–250 ppm, TDS under 1,500, cyanuric acid 0–50 ppm |
| Holder Included | No |
| Holder Care | Lubricate the holder O-ring twice a year with silicone lubricant |
| Estimated Supply | One 4-month mineral cycle and one bromine cartridge (about 2 to 4 weeks) |
| Mineral Cartridge | Blue, 2.05 oz (58 g), silver chloride 0.5%, EPA Reg. No. 53735-11 |
| Mineral Setting and Life | #6, replace every 4 months or at each drain and refill |
| Bromine Active Ingredient | BCDMH (1-bromo-3-chloro-5,5-dimethylhydantoin) |
| Bromine Setting | 0 to 6, matched to hot tub gallons (200–600) |
| Bromine Cartridge Life | About 2 to 4 weeks each, replace when empty |
| Target Bromine Level | 1.0–2.0 ppm, at least 1.0 ppm at all times |
| Refillable | No |
| Recommended Shock | FROG Maintain non-chlorine shock, weekly or as needed |
| Hazard Classification (SDS) | Bromine: Danger, corrosive and oxidizer. Mineral: Caution, very toxic to aquatic life |
| Manufacturer Part Number | 01-14-3812 (mineral) and 01-14-3829 (200 g bromine) |
| Store SKU | Serene 2pack Mineral and 200g Brom |
| UPC | Not specified in reviewed product details |
| Image Alt Text | FROG Serene In-Line refill with one blue mineral cartridge and one green 200 g bromine cartridge |
How to Change FROG Serene In-Line Cartridges
- Turn the jets off: FROG's In-Line manual says not to open the cap while the jets are on. Open the In-Line cap and set it aside.
- Remove the holder: Push the cartridge holder down and turn it counter-clockwise 1/8 turn, then pull it out.
- Set both cartridges: Turn the blue mineral cartridge to #6 and the green bromine cartridge to the setting chart number for your hot tub's gallons.
- Snap them into the holder: Mineral goes in the top area marked "Minerals" and bromine in the lower area marked "Bromine or SmartChlor," lining up each cartridge's indent with the raised area on the holder.
- Lock the holder back in: Line up the holder arrow with the system arrow, push down past the tabs and turn clockwise until it stops. Tug up gently to confirm it is locked, then replace the cap.
- Test and fine-tune: Test daily for the first week and move the bromine cartridge one setting per day until it holds 1.0 to 2.0 ppm.
FROG Serene Bromine Cartridge Setting Chart
| Hot Tub Size | Bromine Cartridge Setting |
|---|---|
| 200 gallons | 0 |
| 250 gallons | 1 |
| 300 gallons | 1 |
| 350 gallons | 2 |
| 400 gallons | 3 |
| 450 gallons | 4 |
| 500 gallons | 5 |
| 550 gallons | 5 |
| 600 gallons | 6 |
From the FROG Serene Floating and In-Line manuals. The blue mineral cartridge always goes on #6. For the first week, test daily and move the bromine cartridge up or down one setting per day until the strip reads 1.0 to 2.0 ppm bromine.
Compatibility Notes
Before You Buy
- Made for hot tubs with a built-in FROG Serene In-Line holder. FROG lists select Marquis, Caldera and Hot Spring models, and dealers also list Artesian.
- Check that your holder says Serene. FROG @ease In-Line hot tubs use SmartChlor and their own mineral cartridge instead.
- The green 200 g bromine cartridge in this refill is the larger size, made mainly for in-line holders. FROG Serene bromine cartridges of either size, yellow 150 g or green 200 g, work in both the In-Line holder and the Floating System floater.
- One bromine cartridge lasts about 2 to 4 weeks, while the mineral lasts 4 months, so plan on extra green cartridges before the next mineral change.
- The in-line holder is part of your hot tub and is not included.
Which FROG Serene Cartridge Do I Need?
| Cartridge | Made For | Replace |
|---|---|---|
| FROG Serene Mineral Cartridge (blue) | Serene Floating and Serene In-Line | Every 4 months, or at each drain and refill |
| FROG Serene Bromine Cartridge, 150 g (yellow) | Serene Floating and Serene In-Line | When empty, about every 2 to 4 weeks |
| FROG Serene In-Line Bromine Cartridge, 200 g (green) | Mainly Serene In-Line (also fits Floating) | When empty, about every 2 to 4 weeks |
| FROG Serene Cartridge Kit (1 blue + 3 yellow) | Serene Floating or In-Line refill | One mineral cycle plus three bromine changes |
| FROG Serene In-Line Refill (1 blue + 1 green) (this listing) | Serene In-Line refill | One mineral cycle plus one bromine change |
| FROG @ease cartridges | FROG @ease systems only | Separate SmartChlor system, not interchangeable with Serene |
Colors help you tell them apart: blue is always the mineral, yellow is the 150 g bromine and green is the larger 200 g bromine, made mainly for in-line holders. Either bromine size fits both Serene systems.
Why Choose the FROG Serene In-Line Refill
It pairs the two genuine cartridges your built-in Serene holder takes, so one order covers a fresh mineral cycle and your next green bromine cartridge. Shop the full FROG Serene line, or compare every hot tub bromine option at HotTubPirate.com.
Ideal For
- Marquis, Caldera and Hot Spring Serene owners
- Built-in FROG Serene In-Line holders
- The 4-month mineral change
- Hot tubs up to 600 gallons
- Shoppers who want free shipping
Frequently Asked Questions
What is in the box?
Two cartridges: a blue FROG Serene Mineral Cartridge for the top of the holder and a green 200 g FROG Serene In-Line Bromine Cartridge for the bottom. Your built-in holder is not part of it.
Which hot tubs use the FROG Serene In-Line system?
FROG lists select Marquis, Caldera and Hot Spring models with a built-in FROG Serene holder. Dealers also list Artesian. Look for the FROG cap on top of the spa.
Where does each cartridge go in the holder?
The blue mineral snaps into the top area marked "Minerals." The green bromine goes in the lower area marked "Bromine or SmartChlor," with each indent lined up on the raised area.
How do I take the in-line holder out?
With the jets off, open the cap, push the holder down and turn it counter-clockwise 1/8 turn, then pull it straight out.
Can I open the In-Line cap with the jets running?
No. FROG's In-Line manual says do not open the cap while the jets are on. Turn them off first.
Will one bromine cartridge last as long as the mineral?
No. The green bromine cartridge lasts about 2 to 4 weeks and the mineral 4 months, so you will need more green cartridges before the next mineral change.
Can I use the yellow 150 g cartridge in my in-line holder?
Yes. FROG's 2026 catalog lists the yellow 150 g cartridge for the In-Line System too. The green 200 g holds more bromine, so it may need changing less often.
Why does the in-line system use a 200 g cartridge?
FROG says the In-Line System utilizes a special 200 g bromine cartridge. Dealers note it holds about a third more bromine than the yellow 150 g cartridge.
What settings do I use in an in-line holder?
The blue mineral always goes on #6. Set the green bromine by gallons, from 0 at 200 gallons to 6 at 600, then adjust one step a day until it reads 1.0 to 2.0 ppm.
Does the in-line holder need any maintenance?
Yes. FROG's In-Line manual says to lubricate the holder O-ring twice a year with a silicone lubricant.
How long should I wait between balancing steps on an in-line hot tub?
The In-Line manual says to add one balancing chemical at a time with the jets on and wait 6 hours before testing again.
What pH range does FROG give for the In-Line system?
7.2 to 7.8, with total alkalinity at 80 to 120 ppm and hardness at 150 to 250 ppm. Adjust alkalinity first, then pH.
Where can I get extra green bromine cartridges?
The green 200 g FROG Serene In-Line Bromine Cartridge is sold on its own and in a 3-pack, so you can keep spares for the weeks between mineral changes.
Should I buy this or the in-line kit with 3 bromine cartridges?
This refill is one of each. The in-line kit adds two more green bromine cartridges, which better matches the 4-month life of the mineral.
How do I know the holder is locked back in?
Line up the holder arrow with the system arrow, push down and turn clockwise until it stops. FROG says to pull up gently; if it stays put, it is locked.
Safety Notes
Handle With Care
- The bromine cartridges are labeled Danger: corrosive, causing severe skin burns and eye damage. Wear gloves and eye protection when you handle or drain them.
- Do not open, break or refill the cartridge, and do not handle a damaged cartridge without protective gear.
- Strong oxidizer. Keep it away from heat, flames and combustible materials, and never mix it with other chemicals.
- Do not use it in a feeder or other device that has been used with calcium hypochlorite.
- The blue mineral cartridge carries a Caution signal word and is very toxic to aquatic life. Do not empty it into drains or ponds.
- Store all cartridges in their original packaging, tightly closed, in a cool, ventilated place (bromine at or below 86°F), locked up and away from children and pets.
Product Documents
Download the FROG Serene In-Line System manual for holder removal and cartridge placement, plus the official Safety Data Sheets for the mineral and bromine cartridges.