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Spa Sanitizers
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Your choice of sanitizers is one of the most important decisions you will make as a spa owner.  Our comparison guide will help you make the right choice.

We recommend spa purifier systems which meet stringent standards for effectiveness in hot tubs. The spa purifiers in the chart below are the best we have found.  One of them is perfect for you.

Hot Tub Sanitizer Comparison Chart
(other systems for hot tubs are also reviewed below)

Sanitizer Technology Test
Effectiveness Economy Ease
of Use
Bromine Tablets Halide Yes No Excellent Good Good
Cleanwater Blue Copper Ion Yes Yes Excellent Excellent Excellent
Nature2 Silver Catalyst No Yes Very Good Good Good
Spa Frog In-filter Mineral No Yes Very Good Good Good
Saltron Mini Salt System Yes Yes Excellent Excellent Excellent
Other Systems --the good, the mediocre, and the ridiculous (facts about them below).

Bromine Tablets

Bromine tablets

Dispener float for bromine tablets

Bromine is a member of the chemical family of halogens, which also includes chlorine. This family of products kills microorganisms including bacteria by attacking their cell walls through oxidation.  They destroy the enzymes and structures inside these cells, which then renders them harmless.

Bromine and chlorine are the most widely used sanitizers for hot tubs and swimming pools.

Bromine tablets for hot tubs are loaded into, and then metered out via a convenient Floating Bromine-Chlorine Feeder such as this adjustable one.

How to use Bromine Tablets in a Floating Feeder


Our Bromine Tablets are EPA registered, an excellent sanitizer, and are relatively inexpensive to use.  It is easy to monitor the bromine level using Bromine 3-way Test Strips to assure proper sanitation. With our floating feeder, bromine can be used in virtually any spa.  Bromine is superior to chlorine in that once free chlorine is combined with waste, it has no further sanitizing capability.  Bromine can be reactivated with OxySpa non-chlorine shock


Although most people prefer its milder odor to that of chlorine, bromine is not odor-free.  Some people may have a sensitivity to bromine.  It tends to dry the skin in some individuals.  Recently there have been some health concerns raised regarding halogen sanitizers.  Bromine degrades upon exposure to sunlight.  Direct contact may cause discoloration of jewelry. Requires frequent testing and adjustments.


For initial effectiveness, Granular Bromine should be added at startup to assure an immediate bromine bank or reserve.  Requires regular shocking with OxySpa. Comparable in cost to other systems.  Actual cost will depend on spa size and use pattern. Read and follow all product label directions and cautions.

Cleanwater Blue System

Cleanwater Blue Bactericide-Algicide Cleanwater Blue is a unique EPA registered liquid bactericide/algicide. It is mineral product which kills bacteria and algae by introducing copper ions into the water.

These ions, delivered by way of its proprietary carrier molecule: CW-286, disrupt the cell structure and chemical makeup of microorganisms, eliminating them in a safe way.

Since ancient times, drinking water vessels were often made of copper to help keep it fresh.  And while crossing the plains, American settlers put copper pennies in their water barrels to inhibit stagnation, although no one really understood why or how it worked at the time.   copper water vessel
Cleanwater Blue molecule Now the purifying properties of copper have been taken a huge step further. A unique molecular activity-enhancer: CW-286, has been developed which radically boosts copper's purification power in a new way. The CW-286 carrier molecule has numerous negatively charged attachment points which hold Cleanwater Blue's positively charged copper ions, and keep them highly potentiated and biologically active.

When bacteria or algae contact potentiated Cleanwater Blue CW-286 molecules, copper ions are released which they quickly absorb. This destroys microbes by disrupting their cell structure.


Cleanwater Blue is odorless and an excellent bactericide.  It also eliminates algae, so there is no need to buy a separate algicide.  The liquid is concentrated, so it's very inexpensive to use.  It is easy to monitor the copper ion level using Copper 3-way Test Strips to assure proper sanitation.  Cleanwater Blue will not dry or irritate skin, cause eye redness, or fade bathing suits.  Unlike bromine or chlorine, this product will not degrade spa cover vinyl or floating thermal blankets, nor will it degrade liners in soft spas, or cause discoloration of jewelry.

Spa water properly treated with Cleanwater Blue is safe to people and pets, since the copper level required in your hot tub is actually lower than the standard set by the EPA for drinking water.  Depending upon your spa size and use pattern, one bottle can last up to 6 months. Very low maintenance effort-- water is tested and adjusted just twice a month.


Although Cleanwater Blue has no significant disadvantages, it is not compatible with conventional stain, scale, and metal reducers, since these products will reduce the beneficial copper ions.  Use only Cleanwater Purge stain & metal inhibitor with Cleanwater Blue. Do not use synthetic clarifiers with this product.


Prepare water with Cleanwater Prep calcium sequestrant.  Requires regular shocking with OxySpa non-chlorine shock. Ozone compatible. Compatible with chlorine (and bromine), so Dichlor Granular Chlorine may also be used at startup, and as an occasional shock if needed. Sea Klear Natural Clarifier is the recommended clarifier. Read and follow product label directions and cautions. Product must be stored above 32° F.  Read more about Cleanwater Blue (pdf)

Nature2 Cartridge

Installation of Nature 2 spa wand The Nature 2 spa purifier unit fits inside your hot tub's filter cartridge. It contains a silver catalyst-- crystals inside of a plastic cartridge.  It works by producing positively charged ions that attack and destroy the negatively charged cells of microorganisms, as water flows through the cartridge.


Nature2 is very good mineral purifier with a reasonable cost to use.  It is odorless, will not dry or irritate skin, cause eye redness, or fade bathing suits.  Nature2 is safe to people and pets. Unlike bromine or chlorine, Nature 2 will not degrade spa cover vinyl or floating thermal blankets.


There is currently no practical way for users to test for silver ion content, so care must be taken to ensure proper sanitation.  Will not work with all spa filters. (Minimum required filter length is approx. 7".  Minimum filter hole diameter is 1-1/4").  If your filter is too small to accommodate the Nature2 unit, you cannot use this system. 


Requires regular shocking with OxySpa. Sea Klear is the recommended clarifier. Not compatible with bromine, so if converting from bromine, be sure to drain and clean your spa prior to use of Nature2. Requires circulating of your spa water at least 4 hours per day. Lasts 4 months.  Upon startup, and when water quality problems arise, water should be shocked with Dichlor Granular Chlorine. Read and follow all product label directions and cautions.

Spa Frog In-Filter

The Frog mineral purifier in-filter stick is a very good mineral product, and must be used in conjunction with a residual bromine or chlorine sanitizer.

Some spas come factory-equipped with this same concept in an in-line, in-spa design.  We have Spa Frog In-Line Refill Cartridge Kits.   Spa Frog Inline Cartridges

Saltron Mini

These saltwater-based systems generate chlorine by passing a mild electric current through salt water, between two plates. Salt (sodium chloride), which is added to the spa water, is the source of the chlorine for the process.

Easy Installation

Although salt systems are gaining huge popularity in pools, until now, we did not recommend their use in spas for several reasons. The equipment was previously very expensive, and required modification to the spa's plumbing which would void your warranty. Now there is an effective, eco-friendly salt system designed for hot tubs.

A reliable, practical, easy to install, and affordable plug-in salt system for spas is now available: Saltron Mini.

Other Systems
(What you need to know before trying them)


We do not recommend packaged chlorine as a primary spa sanitizer. It's fine for use as an occasional shock, but if you choose to use it for sanitizing, select the chlorine form that is suitable for spas: Dichlor granular or chlorine produced from a chlorine generator. Since packaged dichlor does not come in tablet form, and cannot be used in a floating tablet dispenser, your spa will have to be more frequently dosed and tested when using that form.  NOTE: Trichlor and CalHypo tablets are approved for pool use only.  Household bleach is not suitable or approved for use as a spa sanitizer. 


Clarathon ozonator kit
CD Ozonator Kit from AquaSun

Ozonators are excellent devices for helping to maintain good hot tub water quality and purity, but they are not standalone sanitizer systems.

Ozone works in conjunction with your sanitizer system to improve and purify the spa water by oxidizing soap, deodorant, hair spray, cologne, makeup, perfume, body lotion, hand cream, sun tan lotion, saliva, and urine.


There are several brands of Biguanides on the market (chemical name: polyhexamethylene biguanide or PHMB) such as BAQUACIL® and SoftSwim®. We do not offer them because of lack of compatibility with other spa chemicals, and because they tend to be more expensive than other sanitizer systems.  Their use may require other proprietary companion products such as special filters cleaners, etc.  Biguanides may erode certain plastics such as polycarbonates.  Many users report problems with algae slime that are difficult to eradicate.


This silver-based liquid product is no longer supported by us.  We recommend Cleanwater Blue as an excellent replacement.

Electric Spa Ionizers

Spa Ionizer These units produce metal ions by passing an electric current through spa water between two electrodes. As the water passes over them, ions are displaced from the electrode plates and circulated. They are installed by cutting and splicing into your spa's plumbing system.
We do not recommend electric ionizers for spas for several reasons. They have a substantial initial equipment cost and usually require modification to the spa's plumbing, which may void your warranty. These systems can be prone to maintenance problems. They also require periodic replacement of the electrodes as they are depleted. The ion levels can also be problematic to monitor for proper sanitizer level.  Since these systems run on electricity, this cost should also be factored when evaluating them. Some promoters of these ionizers tout them as "chemical free" systems. This is a falsehood, since by definition, metal ions in water are chemicals.  They merely use the spa as a mini chemical factory to produce the ions electrically, rather than pour them from a bottle. A chemical shock must still be added to oxidize organic matter and dead cells.

Hydrogen Peroxide

We do not recommend hydrogen peroxide for use in home spas for a number of reasons.  Unlike the 3% drugstore variety, commercial-grade peroxide strong enough to be effective in pools or hot tubs ranges from 25% to 35% concentration. It can be dangerous to store, transport, and handle.  Although it does a fair job of controlling bacteria at 30-40 PPM, it must be monitored very closely, because at excessive levels it can burn lung and eye tissue. It can prove to be more expensive to use than other systems.


Magnets Unbelievable but true-- and barely worth mentioning: bolt-on magnets sold to consumers with claims that they reduce spa chemical usage, stabilize pH, and reduce odors by "magnetizing" the hot tub water. 
Magnetic spa water treatment is junk science, akin to snake oil. There is no valid empirical data to support these claims. Avoid these dubious devices. They are a worthless waste of money.

Rainforest Blue

We do not recommend this product since the introduction of the advanced, EPA-registered Cleanwater Blue system. We've heard reports of problems with staining, and performance issues, especially with well water or water with significant calcium content. These problems have been overcome with the introduction of Cleanwater Blue, which has a highly advanced carrier molecule: CW-286. This carrier optimally potentiates the copper ions, and works in unison with Cleanwater Prep to sequester excess calcium.  Cleanwater Blue bactericide/algicide also requires less monitoring and testing-- adjusted just twice a month. NOTE: Rainforest Blue is no longer legal for sale in most states.

spa customers write  Consumer Reviews
Cleanwater Blue Pro Starter Kit
"Received the Cleanwater [Blue] kit of supplies last week, and I must say it has a lot of stuff in it for the money.  We emptied the spa and refilled it according to the directions have been using it for a couple of days.  My family is already complimenting me on the lack of bromine odor.  We no longer have to shower again AFTER getting out of our spa! "

M. Fellows
Aberdeen, SD

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