How-To Guides | Sanitizers - Comparison guide to help you choose wisely

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

(other systems for hot tubs are also reviewed below)

Bromine Tablets

  • Type: Halide
  • Test Available: Yes
  • Maintenance Level: High
  • Effectiveness: Excellent
  • Cost: $$
  • Ease of use: Good

Cleanwater Blue

  • Type: Copper Ion
  • Test Available: Yes
  • Maintenance Level: Low
  • Effectiveness: Excellent
  • Cost: $
  • Ease of use: Excellent


  • Type: Silver Catalyst
  • Test Available: No
  • Maintenance Level: Low
  • Effectiveness: Good
  • Cost: $$
  • Ease of use: Good

Spa Frog In-filter

  • Type: Mineral
  • Test Available: No
  • Maintenance Level: Low
  • Effectiveness: Good
  • Cost: $$
  • Ease of use: Good

Saltron Mini

  • Type: Salt System
  • Test Available: Yes
  • Maintenance Level: Low
  • Effectiveness: Excellent
  • Cost: $$$
  • Ease of use: Moderate

Other Systems --the good, the mediocre, and the ridiculous (facts about them below).

Bromine Tablets

Bromine is a member of the chemical family of halogens, which also includes chlorine. This family of products kills microbes 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 are loaded into a handy Floating Bromine Feeder for mixing with the water.


Our Bromine Tabs are EPA registered, an excellent sanitizer, and are relatively inexpensive to use. It is easy to monitor the bromine level using Bromine 4-in-1 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 and on some individuals, it tends to dry the skin.

Bromine degrades upon exposure to sunlight. Direct contact may cause discoloration of jewelry. Requires frequent testing and adjustments.

Notes: 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. Read and follow all product label directions and cautions.

Cleanwater Blue System

The Cleanwater Blue system 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 disrupt the cell structure and chemical makeup of microbes, eliminating them in a safe way.

Since ancient times, drinking water vessels were often made of copper to help keep it fresh. American settlers used to put copper pennies in their water barrels to keep it from going stale. No one at the time really understood why or how it worked.


The Cleanwater Blue system 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. It won't harm spa cover vinyl, floating thermal blankets, or soft spa liners like bromine or chlorine can.

Cleanwater Blue in spas is safe because the copper levels needed are less than the EPA standards for drinking water. Depending upon your spa size and use pattern, one bottle can last up to 6 months. Very low maintenance - water is tested and adjusted just twice a month.


Cleanwater Blue has no major drawbacks. Regular stain and metal reducers will reduce the helpful copper ions, so stick with Cleanwater Purge stain & metal control. Use only natural clarifiers with this product.

Notes: Prepare water with Cleanwater Prep calcium sequestrant. Requires regular shocking with OxySpa non-chlorine shock. Ozone compatible.

Works with chlorine (and bromine), so Dichlor Granular Chlorine can be used at startup, and as occasional shock if needed. Chitosan Natural Clarifier is the recommended clarifier.

Read and follow product label directions and cautions. Product must be stored above 32° F.

Nature2 Cartridge

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. As water flows through the cartridge, positively charged ions kill negatively charged cells of microbes.


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 no practical way to test for silver ions in the water. 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.

Note: Requires regular shocking with OxySpa. Chitosan Natural Clarifier is the recommended clarifier. Nature 2 is not compatible with bromine.

If  you're 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 Spa Frog in-filter mineral stick is a great product. Use it with normal bromine or chlorine sanitizers for crystal clear water.

Some spas come factory-equipped with this same concept in an in-line, in-spa design. For these spas, we offer Spa Frog In-Line Refill Cartridge Kits.

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.

While salt systems are popular in pools, until now, we didn't suggest them 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 chlorine generator.

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 shock once in a while, but if you use it as a sanitizer, use Dichlor granules.

Another option is the chlorine from the Saltron Mini chlorine generator. Since packaged dichlor does not come in tablet form, you can't use a floating tablet dispenser. That means more frequent dosing and testing 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.


Ozonators are great devices for improving water quality, but they should only be used as a secondary sanitizer.

Ozone works with your primary sanitizer by oxidizing beauty products and bodily fluids in the spa water. 


There are several brands of Biguanides on the market (chemical name: polyhexamethylene biguanide or PHMB) such as BAQUACIL® and SoftSwim®. We don't offer them since they are more expensive and don't work with many spa chemicals. 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 the Cleanwater Blue system as an excellent replacement.

Electric Spa Ionizers

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 just use the spa as a mini chemical factory.

Ionizers make ions with electricity, instead of pouring 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.

It does an ok job of killing bacteria at 30-40 PPM, but you've got to watch it very closely. At very high levels, it can burn lungs and eyes. It can also cost more to use than other systems.


This far-fetched product is barely worth noting. Bolt-on magnets that claim reduced chemical use and less odor 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.

Cleanwater Blue Bactericide/Algicide

"Received the Cleanwater Blue last week, and I'll say, it's great! 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