FROG Serene® In-Line System (formerly SPA FROG)

Clean, serene, and customized

Average Rating: 5 11 Reviews

Our FROG Serene System is so popular, some spa brands have built it directly into their spas. It makes hot tub care even easier, and your hot tub experience even more luxurious. With FROG Serene, there’s no measuring out the right amount or constantly adding chemicals.  You simply replace your FROG Serene cartridges when used up and enjoy weeks of Fresh Mineral Water®.  That’s what FROG Serene provides with minerals and a low level of bromine that makes water feel softer and look crystal clear.

Pool Foreground Hot Tub Foreground
50% Less

Lower your bromine use up to 50%* with FROG minerals

Bromine Disolves

Unlike chlorine, bromine slowly dissolves in hot water so it’s easier to regulate. Plus far less odors.

Icon 50% Less

Bromine is less impacted by pH swings ensuring sanitizing effectiveness

Soft Feeling

Soft feeling water that’s easier on skin, swimsuits and spa surfaces

Set and Forget

Just set it and forget it for weeks at a time

Money Back Guarantee

Money back guarantee

Serene On Towel

Video Introduction to FROG Serene In-Line System

Serene Cartridges

Additional Information

The FROG Serene Fresh Mineral Water In-Line System is part of the hot tub’s plumbing, with an easily distinguishable and convenient cap for top loading of the mineral and bromine cartridges. A simple twist and the cartridge basket is removed from the hot tub for quick and easy cartridge replacement. The entire process takes less than a minute. The minerals last a full four months set wide open, while the bromine usually lasts around three weeks with adjustable settings to meet each hot tub’s needs.

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What size hot tub will FROG Serene work in?

Hot tubs 150 to 600 are perfect for FROG Serene.

How does FROG Serene compare to other bromine floaters or using chlorine?

If you are tired of smelly chlorine odors and having to spoon in chemicals every time you use your hot tub, FROG Serene is for you. FROG Serene is not just bromine.  It contains FROG minerals that destroy bacteria so you need up to 50% less bromine. Plus with the In-Line System everything is tucked away but with easy access when you need it.

How long do the mineral and bromine cartridges last?

The mineral cartridge lasts four months or whenever the hot tub is drained and refilled. The bromine cartridge lasts 2-4 weeks.

Which hot tub brands have the FROG Serene In-Line System?

Marquis Spas, Caldera Spas and Hot Springs Spas all have the in-line system installed on select hot tub models at their factory.

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* Compared to the minimum ANSI recommended bromine or chlorine level of 2.0 ppm for a hot tub

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See Our Customer Reviews

  1. James Ables

    Rating: 5

    I normally do not take surveys like this or comment however; I have to write about the telephone conversation that I had with Dan. I could not have been happier. My inline Frog carrier’s handle broke off and of course I was furious. I called customer service and spoke with a person named Dan. I informed him of my frustration and he explained to me some of the things that I may have been doing wrong, but he said it in a way that was non-confrontational. He asked if I had put lubricant on the O-ring at the top of the carrier, I didn’t even know I was supposed to do that. He informed me that if the O-ring stays well lubricated the carrier will not be that hard to open. He also informed me that a lot of downward pressure is not needed to unscrew the carrier from the hot tub. housing. Another thing that may have been common sense is that you should make sure the hot tub is not running when replacing the cartridges. I gave him a few suggestions that I thought would be helpful on their website. When I purchased my hot tub, the inline frog system did not have any instructions as to how to care for the system. Dan sent me a new carrier and included some of the lubricant in the package. His customer service and positive attitude was a breath of fresh air that I needed because of my frustration. If you are having ANY problems with your FROG system give him a call. I would say that you will get the same quality of care as I did. Love their products!

  2. Steven Bower

    Rating: 5

    Is there a significant difference in the yellow and green cartridges? They look basically the same.

  3. Richard Svendsen

    Rating: 4

    Could you provide me the length, width of this cartridge to see if it would work in my older spa(no longer made)

    • Tom Sager

      Hi Richard,

      As long as you have the Spa Frog In-Line housing, the cartridges haven’t changed in size. Therefore, they will fit into their housing.

      Please let me know if you have any additional questions or concerns. Additionally you can contact Dan or Allyn on our customer service team directly at 800-222-0169.

      Thank you!

  4. David

    This product is absolutely the best solution to your hot tub enjoyment! I have a Marquis spa and with the in-line system there is nothing floating in the water. There is no chemical odor, relatively no maintenance and most importantly, clean, FRESH water. Very, very, impressed!

  5. Phil Johnson

    Rating: 5

    The in line system works great I’ve had our Calder hot tub for 14months. The only prob I’ve had was the cartridge holder is falling apart because of the chemicals. Need to order one. I give your system 5 stars.

    • Gary Hinks

      I too am having this problem. Is there a way to order some of these holders direct from the manufacturer as i see i will need to have on hand as an on going
      replacement ritual.

      • Tom Sager

        Hi Gary,

        Please call Dan or Allyn on our customer service team at 800-222-0169 who can order you a new cartridge holder.

        Thank you!

  6. Dan

    Rating: 5

    Excellent customer service and product support. I contacted King looking for information on obtaining a replacement in-line assembly and within a few quick exchanges, was informed a replacement was being sent out. Impressive!

  7. Joe Lidsay

    Rating: 5

    Very Happy with the spa frog system, have had my Caldera Salina spa for a month.

  8. David Thomson

    Should have also mentioned — the part was sent all the way from the USA to the UK next day delivery. Thanks again

  9. David Thomson

    Rating: 5

    Excellent system, and very easy to use. Had an issue with the cartridge holder, that being honest was not an issue for king technology to resolve but my spa supplier. King Technology jumped right in and sent me a replacement holder before my supplier even had a chance to reply to my emails. Excellent service and backup.

  10. Mitch Elson

    Rating: 5

    We have a Marquis Spa that has an in line system for the Spa frog mineral and bromine cartiridges. Works absolutely fantastic. No floating devices and the water is easy to care for and always crystal clear.

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