What is a Hot Tub Sanitizer and Which Sanitizer is the Best?

Posted by

A hot tub sanitizer kills bacteria and purifies the water. The sanitizer is the most critical component to a healthy hot tub experience.
Hot Tub Sanitizers

There are many sanitizers on the market. Some are great, some are mediocre and some are terrible. Below, I’ll take you through the different sanitizing options and the pros and cons of each.


Chlorine is the most widely used sanitizer for pools. Because it does not come in tablet form, it is not a suitable stand-alone sanitizer for spas, as the granules dissipate too quickly.

Chlorine is a great shock for hot tubs and is commonly used in conjunction with mineral sanitizers, burning off dead organic matter and preventing cloudy water.


Bromine is the most widely used hot tub sanitizer. It comes in tablets which can be inserted into a floating bromine feeder and provide continuous sanitation to the water.

While very effective at killing bacteria, some people may have a sensitivity to bromine. Some individuals experience dry or irritated skin and find the chemical odor of bromine to be overwhelming. Learn more about bromine.

Cons of Chlorine & Bromine

Excessive use of halogen sanitizers (chlorine or bromine) can bleach and damage the underside of the spa cover, fade swim suits and even pit the hot tub shell.


Mineral Sanitizers

There are a couple “alternative hot tub sanitizers” on the market that use copper or silver ions to sanitize spa water. Many people switch to mineral sanitizers because they are odorless, more natural, and do not fade swimsuits or damage spa covers.

  • Cleanwater Blue – Cleanwater Blue is an EPA registered liquid bactericide/algaecide made from copper ions. These ions disrupt the cell structure of microorganisms, eliminating them in a safe way. The science behind Cleanwater Blue dates back to ancient times, when drinking water vessels were made from copper to help keep the water fresh. While crossing the plains, American settlers often put copper pennies into their water barrels to prevent stagnation.

Cleanwater Blue Sanitizer

  • Nature 2 – Nature2 is an EPA Registered cartridge containing silver minerals, which you can put in your filter cartridge or in the filter housing. As water passes through the Nature2 cartridge, positively charged silver ions disperse in the water, and destroy negatively charged cells of microorganisms. Like Cleanwater Blue, this system is a great alternative for people who have a bromine sensitivity and is comparable in price.

Nature2 Mineral Sanitizer

Cons of Mineral Sanitizers

While there are no major cons to using mineral sanitizers, using test strips with these systems can be somewhat tricky. To date, there is no practical way for users to test silver ion content, so care must be taken to follow dosage instructions. However, copper test strips are available for the Cleanwater Blue system.

Bromine/Chlorine + Mineral Sanitizers

  • Spa Frog – Spa Frog sanitizing systems combine minerals and a small amount of bromine to achieve sanitization in hot tub water. By incorporating minerals, the amount of bromine needed is greatly reduced. Spa Frog systems are a great option for people that like the test-ability of bromine and the benefits of mineral sanitizers.

Spa Frog Mineral Sanitizer

  • PoolRX – Despite its name, PoolRX is a great mineral sanitizer for spas. This product works synergistically with a constant low level of chlorine.

Pool RX


Ozonators, or ozone generators, are add-on components in hot tubs that distribute ozone through the air lines. Ozone works to break down contaminants in hot tubs by oxidization, destroying bacteria, soap residues and other undesirable particulate on contact.  Ozone also frees up spent chlorine and bromine particles, enabling them to be reused again and again and allowing you to use far less chemicals to maintain sanitation.

Ozone has a very short half-life in water (about 15 minutes) and must be used in conjunction with a sanitizing agent, such as Bromine, Cleanwater Blue or Nature 2.
Aqua Sun Ozone

Cons of Ozone

Excessive ozone can cause damage to the underside of spa covers and thermal blankets.

Salt Systems

Saltwater based systems, such as the Saltron Mini, generate chlorine by passing a mild electric current through salt water. Salt, which is added to the spa water, is the source of the chlorine which acts as the sanitizer with this system.
Salt Systems

The ease of use with these systems makes them very popular. Many people also experience softer, more moisturized skin after soaking in a hot tub equipped with a salt system.

The low salinity level required with these systems does not corrode spa equipment. Learn more about salt systems.

Cons of Salt Systems

The cells which generate the chlorine require some cleaning maintenance.


Biguanide sanitizers are commonly hydrogen peroxide based and require proprietary companion water balancing products.

Cons of Biguanide Sanitizers

Biguanides are known to erode certain plastic components, such as jets, causing them to no longer stay in place. Biguanides and their proprietary companion components are significantly more expensive than most other sanitizing systems. Many people report coughing and burning sensations in the lungs and eyes after inhaling steam in hot tubs treated with biguanide sanitizers. Commercial Hydrogen Peroxide used in hot tubs can be dangerous to store, handle and transport. Biguanide sanitizers often fail to prevent algae slime.

Mystery Ingredient Systems

There are several mystery ingredient “water treatments” on the market which claim that you can “throw away all of your other chemicals” and “use this product and never test your water again”.

Silk Balance

Beware! These products survive by using irresponsible and dangerous marketing. The small print on these products state that they do not kill bacteria.  The truth is that these products are mostly comprised of dissolved salts in water. Truly not worth the $100+ price tag.

If it sounds too good to be true, it usually is.

So, Which is the Best?

It is clear that mineral systems are gaining huge popularity. Being that they are odorless, gentle on the skin and hot tub equipment, and comparable in price to chlorine/bromine sanitizing systems, it’s not hard to understand why.

Do you have questions about your hot tub water maintenance? Comment below for expert assistance!


  1. Hi Cd,

    Thank you for checking with us. No, you do not want to use Nature2 in a saltwater tub. Your saltwater system is already the sanitizer for your spa water, so adding the Nature2 would be a waste of your money.



  2. I have read your entire list of responses and I still do not know which system is best. It seems it boils down to the choice between the Frog System and Ozonators. So, straight forward, which is best?


  3. Hi Larry,

    Of these two choices, the Floating Spa Frog System is going to be the best option of sanitizer. This system contains mineral and bromine cartridges that are pre-filled and will need to be replaced when depleted. The bromine cartridge can be adjusted to meet your sanitizing needs of at least 1.0 ppm bromine level. This system is far easier to maintain than bromine tablets and with the mineral cartridge it uses 50% less bromine.

    An ozonator is not a standalone sanitizing system but works with bromine, Cleanwater Blue or Nature2 to improve the water by oxidizing organic and inorganic contaminants. Chemicals used are reduced by 50 – 75%, but are still necessary to purify the spa water.

    Regardless of choice, shocking the spa is recommended at least once per week or after each use to allow the sanitizer to perform at peak efficiency.

    I hope this helped you decide which sanitizer to choose. If you have any other questions, please let us know.



  4. I have an ion (silver) hot tub cartridge and use both the mps shock and occasionally the ‘up ph’ as the test stip suggests. However, lately we have been getting a lot of suds. We changed the cartridge, cleaned the filter and emptied and refilled the tub. What am I missing?


  5. Hi Judi,
    The suds could be from low pH and Alkalinity, or they could be cause by different lotions or soaps getting in the tub. If the pH and Alkalinity are at the right levels, you might try our Foam Free to get rid of the foam. Using a small amount of Dichlor (Chlorine granules) can also help, and is completely compatible with Nature2, and any other ion sanitizer.
    I hope this helps!


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s