Posted by A hot tub sanitizer kills bacteria and purifies the water. The sanitizer is the most critical component of a healthy hot tub experience.
The Center for Disease Control only recommends a few sanitizers as proper hot tub disinfectants, or “Primary Sanitizers”. These include chlorine, bromine, and a few mineral sanitizers when used in combination with an oxidizer.
Other products that do help destroy microorganisms but are not effective enough to use alone are “Secondary Sanitizers.”
UV is not a primary sanitizer.
Ozonators are not primary sanitizers.
Oxidizers aka non-chlorine shock or MPS are not primary sanitizers.
UV, Ozone, and oxidizers can be noted as chemical reducing aids, but still, require the use of a halogen-based or primary sanitizer.
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
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
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 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.
- 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. This system is a great alternative for people who have a bromine sensitivity and is comparable in price.
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.
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.
- PoolRX – Despite its name, PoolRX is a great mineral sanitizer for spas. This product works synergistically with a constant low level of chlorine.
Ozonators
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, Nature 2, PoolRx or Spa Frog.
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.
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.
Biguanides
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”.
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 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!
Hot Tub Blog | SpaDepot.com 
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.
Thanks,
Mark
SpaDepot.com
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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?
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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.
Thanks,
Rosy
SpaDepot.com
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Thanks very much. This is very helpful.
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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?
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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!
Thanks,
Mark
SpaDepot.com
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Hi, I have a Sundance spa which uses a mineral cartridge(not currently in use). I’ve never had time to research it or use it until now and I’m very interested in using this method. I ordered a new Sundance cartridge and when it arrives I will change my water and start fresh. My question is about bromine – there is a warning that these cartridges aren’t compatible with bromine! So if this is the case will I also have to switch to chlorine as my additional sanitizer? I’ve read that chlorine doesn’t work well in spas so I’m concerned about how to use the mineral sanitizer correctly with chlorine and/or is the info about bromine and minerals is incorrect. Can you advise?
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Hi Frank,
Thanks for checking with us! You’re right on almost all accounts. You cannot use bromine with the mineral sanitizer, that is true. You can use chlorine, and there is a granular chlorine that works great with mineral sanitizers. It’s called Dichlor, or Spa Sanitizing Granules. On our site you can search item codes CA1004 or CA1011, depending on which size you want. With a mineral sanitizer you want to add 1-2 tablespoons of Oxy-Spa (non-chlorine shock) after each use, and you can add about 2 teaspoons of Dichlor once a week, or as needed to clear up cloudiness. I hope this helps, and please let me know if you have any other questions!
Thanks,
Mark
SpaDepot.com
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Just starting to read up on this for alternatives to what we are using. We have a Hot Springs Spa, about 3-4 years old. Have been using the Spa Guard Shock weekly with the Silk Balance and also have the mineral stick cartridge that we put in the filter that gets changed every 4 months….we add the shock and Silk weekly. The Silk has become so expensive I cannot justify using it anymore and am looking for an alternative. We put some Silk Balance in it yesterday and got a heavy yellow film on the top of the tub and it bubbled like bacteria. Skimmed it off, cleaned the filter and the water is slowly becoming un-cloudy but obviously we cannot use that. What is an alternative to the Silk Balance? We have done everything up to this point our tub company suggested but the cost is just becoming crazy. We grew up with swimming pools and it seems keeping those maintained with chemicals was far cheaper than our tub. Suggestions? Help? Thanks, Dave, Texas.
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Hi Dave,
Great question! The Silk Balance is not a mandatory product and you can discontinue use right away. It’s sold as a water softener, pH stabilizer, and a whole host of other claims, but none of those are necessary for clean, clear water.
To get that gross yellow scum (probably biofilm, a bacteria that grows in your plumbing), use Spa System Flush in your tub, then drain and refill. There are some other drain/jet cleaners but the SeaKlear Flush is by far the most effective.
Additionally, your mineral cartridge and shock can be purchased for significantly less. The mineral cartridge is most likely made by the same company as the yellow one in this article, and the only differences between the two is the color of the plastic and the shape of the adapter piece that keeps it from getting sucked into the plumbing.
The shock you are using weekly could either be dichlor or monopersulfate(MPS) or a blend. You are better off using the pure products without fillers, and adding the dichlor (chlorine) as needed and the MPS (non-chlorine) more frequently to deal with oil, lotion, dead skin, sweat and other stuff we leave behind in the hot tub.
There are even very low cost, but very effective, additives that soften the water, keep pH in check and much much more! Choosing these additives individually means you aren’t buying or adding more chemicals than you need.
I highly recommend you look online for products not branded by your dealer or manufacturer. I may represent an online hot tub supply store, but even if you don’t buy with Spa Depot, you will save tons of money and have more choices. Dealers can be great for quick stops in an emergency, but if you are looking to save online is your best bet by far.
Let me know if you would like help creating a new maintenance routine, or if you have any other questions.
Thanks,
Sarah
SpaDepot.com
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I have purchased a new hot tub that has an ozone generator. I used the frog system in my old hot tub but it did not have an ozone generator. Is the frog system compatible with the ozone generator? If not, which sanitizer should be used? Easiest one please!!
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Hi Nancy,
Thanks for reaching out to us about using an ozone generator. You’re in luck, ozone generators are compatible with the Spa Frog Sanitizing System! So you can continue using this system you’re most familiar with. Ozone simply reduces the need for chemicals, so you may see a longer usage period with the Spa Frog System.
Regards,
Rosy
SpaDepot.com
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Based on your grid of benefits each sanitizing system offers- I am thinking of switching from Nature 2 to Cleanwater Blue (less expensive and test strips for the copper) I have recently refilled the hot tub and balanced the PH. I have used granular chlorine and Oxy Spa for a month. Can I switch to Clearwater Blue without draining this water?
A completely different question- we have had this new hot tub for a little over a year and have had several episodes of what I think is white mold. We treated the last hot tub in the same manner and in 10 years never once had this problem. It is a MAJOR deal to get rid of it! I THINK it might be because the new tub has so many diverters that some lines are never on- and then when they are used- its there!! I would appreciate any suggestions you have.
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Hi Patrice,
When switching to any new sanitizing system you’ll want to flush your hot tub plumbing system with Spa System Flush (https://www.spadepot.com/Spa-System-Flush-16oz-P817) then drain and refill the water.
But first, I would suggest you follow these steps to determine if your episodes are white mold or simply excess calcium:
1. Take a sample of the flakey water.
2. Pour 20 drops of liquid bleach into the water sample, gently stir and wait 30 minutes.
3. If flakes are still there, it’s more than likely calcium.
4. If no flakes remain, it could be White Water Mold or biofilm.
Depending on the outcome of this test will determine what you should do next. If it is White Water Mold, then please read this post on how to remove the mold https://hot-tub-blog.spadepot.com/2018/03/16/mold-and-mildew-in-a-hot-tub/.
If it is excess calcium, try using a hose end fill filter (https://www.spadepot.com/Pre-Fresh-Spa-Pool-Water-Fill-Filter-P2666) after flushing and draining your spa. Then use a product such as Spa Defense (https://www.spadepot.com/Spa-Defense-Scale-Preventer-32oz-P2040) to prevent excessive calcium in the future.
Please let us know if you have any other questions!
Thank you,
Rosy
SpaDepot.com
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We need help getting the sanitizer level correct. It is low (15)
We use nature,s choice spa mineral purifier and xtra blue shock.
Thanks
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I have the spa frog inline system and ozone generator, I have stopped using bromine and am now using the Frog silver clonine cartridge. Should I or can I still use the blue mineral cartridge?
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Hi Jan,
When using a mineral sanitizer, there is no need to keep your chlorine level at the standard range. Shocking about once a week is good. If you use your spa daily or don’t shower before use, you may need to up that to 2 times per week.
Thanks,
Sarah
SpaDepot.com
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Hi Larry,
If I understand you correctly, you are switching from the standard Spa Frog system to the @ease cartridges. You will want to use both the silver chlorine cartridge and the blue mineral cartridge, and do not use any other cartridges from the old system.
Thanks,
Sarah
SpaDepot.com
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Are you able to tell me the difference between Theralux Spa Sanitiser and Spa Shock Sanitiser and do they both work in a hot Spa.
Thankyou
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Hi Merle,
The Australia only Theralux appears to be a mixture of Borax, MPS, and clarifier. The Borax is used to control algae, which means it’s geared towards pool use rather than spa use. Many products can be used as a Spa Shock Sanitizer, so it’s hard to compare a product without knowing specifically which one you’re interested in. We do carry hot tub specific product that’s an all in one conditioner, water balancer, shock and clarifier, found here: https://www.spadepot.com/EZ-Spa-Total-Care-2-lb-P836.
Thanks,
Brian
SpaDepot.com
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Hi I am thinking of using clear blue copper ionizer as a primary mineral system. I know you did not review that here. But I am thinking of using it with spa frog, because it is supposed to have some back up Bromine, .6ppm, but without mineral cartridge and an ozonator and occasional non chlorine shock if needed. Do u think this will work? Is it a good plan? Thanks!
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Hi,
The concept of the Clear Blue system is great: utilize copper ions to control bacteria and algae (like our Cleanwater Blue system). If you can handle the installation of the system, which involves cutting and gluing into the plumbing, your plan should work. If you just want to try out a mineral based sanitizer before making the (considerable) investment in the Clear Blue system, try a Nature 2 cartridge or Cleanwater Blue. In my experience, they work every bit as well, cost a fraction of the Clear Blue system, and you don’t have to modify your hot tub.
Thanks,
Brian
SpaDepot.com
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How is ther Inclear bromine salt system? Does it to get rid of the need for clorine,shock,and frequent testing?
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Hi Eric,
The in.clear system is a very good system, producing bromine in much the same way as our Saltron Mini produces chlorine. If your hot tub came with one, that’s great. I’d do some double checking though if you’re thinking about retro-fitting that system into an existing hot tub. The in.clear system does require extensive plumbing modification and a special control system to make it work.
As far as chemistry goes, the in.clear is only producing sanitizer. You’ll still have to shock the water with the same frequency as any other sanitizing system, and test the water periodically to make sure you have the correct sanitizer and water balance levels.
Thanks,
Brian
SpaDepot.com
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Hi, we are wondering which system is safer for our “overall health” in our spa , using chlorine, or the Frog mineral cartridge, we know chlorine is absorbed thru the skin , and are currently using it in our new spa. Thank you, Joe
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Hi Joe,
The chlorine level in well maintained spas is fairly low, at 3 ppm. Still, if chlorine is a concern, Frog cartridges only require a 1 ppm free chlorine level. You’ll have the benefit of less chlorine, and a properly sanitized spa. I’d say it’s the best of both worlds.
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Hi. If using a mineral system with silver, do I only have to shock the tub once a week? I don’t have to add chlorine at other times? What level of chlorine would I need to raise it to to shock it? Thanks!
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Hi,
There are two ways to use the Nature2 mineral sanitizer: No chlorine and low chlorine. For the no chlorine method, simply add chlorine at startup per instructions, then shock after each use with non chlorine shock. Here’s our startup guide that goes over low chlorine: https://www.spadepot.com/docs/KT1005.pdf.
For the regular chlorine method, you’ll add chlorine weekly, and maintain a low 1.0ppm chlorine level.
Thanks,
Brian
SpaDepot.com
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We recently purchased a used hot tub. We ran a line cleaner through it and emptied and cleaned it twice, then put in fresh water and an enzyme system I had read about online. I used the hot tub 3-4 times that first week. The water is really clear, but smells not so great. They said this would be normal the 1-4 weeks until it levels out. The ph is good. But now I am afraid to use it with it smelling off. I was contemplating adding the mineral system as backup. We were hoping to avoid using any chemicals at all. Is this sufficient, or not so much? I’m so overwhelmed with all the information!
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Hi Rachel,
Congrats on the new tub! My suspicion is your cover may be causing the smell. If you haven’t already, remove the foam cores and give the inside and outside of the cover a good cleaning. Here’s a really good article to read about it: https://hot-tub-blog.spadepot.com/2015/01/30/why-does-my-hot-tub-cover-stink/.
Avoiding using chemicals at all isn’t really going to be feasible. Keeping your water properly balanced and sanitized is the highest priority, and is going to require modest chemical use. Remember, properly chlorinated spa water generally has less chlorine in it than tap water. If you have any questions, or would like a real live person to talk to about water chemistry or hot tubs in general, give us a call at 800-823-3638. We’re happy to make sure your tub is safe and ready to use at all times.
Thanks,
Brian
SpaDepot.com
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my swim spa holds 1600 gallons of water, should I use 2 mineral spa sanitizer cartridges.
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Hi Rose,
The Nature2® Spa was designed to sanitize spas up to 500 gallons. That would mean you’d need 3 of them to satisfy your 1600 gallon water capacity. A more economical alternative for your swim spa would be Cleanwater Blue. It would have no trouble keeping up with the extra water. If you have any questions, give our customer care department a call at 800-823-3638.
Thanks,
Brian
SpaDepot.com
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Hi Brian,
We’re in the market for a backyard hot tub and have a generous budget. Would you recommend a saltwater tub as the option with the least chemicals and lowest maintenance? Thanks so much!
Dobrina
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Hi Dobrina,
Great question. All things being equal, I’d recommend looking for a spa that utilizes UV-C plus Ozone technology. There’s less room for error when refilling the spa and getting the chemistry set up versus a saltwater spa. Additionally, with UV-C, you have the option to run zero chlorine, whereas Saltwater spas are designed to create chlorine.
Thanks,
Brian
SpaDepot.com
800-823-3638
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Hi I’ve just bought my first hot tub four months ago, I have tried chlorine and bromine and both are giving me an itchy rash which is surprising as have done a lot of swimming in public pools and didn’t have any bother, I use the tub once a week and shower before i get in, Can i use Nature 2 without any chlorine or Bromine
I have just filled it and put 1 bromine tablet in the floater, can I just stop using Bromine and use the Naure 2 without emptying the tub
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Hi Peter,
You can definitely switch to Nature 2 without doing a drain and refill, though I think the results will be better if you do. Are you sure it’s the Br or Cl causing the irritation? Very often there are other underlying water chemistry issues that are to blame, such as pH too low or too high. Even the kind of shock you use can be the problem. To get a better idea of what’s going on, please give us a call when you have a moment to to some quick tests. We’ll be happy to isolate the problem and get you back into hot water.
Thanks,
Brian
SpaDepot.com
800-823-3638
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Hi, we are picking a new hot tub and looking for a way to be chlorine-free or keep it as low as possible. We also want to stay away from Bromine. Are there tubs that come with both UV-C and Ozone? it seems the brands i see offer one. If we have to pick one, which one would be less maintenance effort (dont care about costs) and which one would reduce/eliminate chlorine more?
thanks a ton! by far this is the most useful thread i found online so far on the subject 🙂
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Hi Paul,
It’s important to note that UV-C and/or Ozone are not sanitizers. You will always have to use a primary sanitizer such as bromine, chlorine, or copper/silver mineral cartridges. UV-C/Ozone oxidize the water, which allows your primary sanitizer to work better. Indeed, with an ozonator you’ll notice that your free chlorine levels stay in the acceptable range for longer than without. Give us a call and we’ll talk about alternative sanitizers with you so you can use the bare minimum of chlorine/bromine.
Thanks,
Brian
SpaDepot.com
800-823-3638
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