Do you know the #1 reason/why MOLD GROWS ON YOUR BOAT SEATS?

Mildew is one of the most common problems with vinyl boat seats. It often grows on seats when boats are covered because it thrives in warm, dark, damp places. Mildew ends up smelling and looking bad, and it can eventually break down the vinyl your seats are made of.  It’s best to take measures to prevent it whenever possible and clean it up quickly once you realize it’s become a problem.

Mold, mildew and the odor can create a huge problem even on boats that appear to be clean and well ventilated. This is because, apart from the visible areas in a boat’s cabin, there are many areas that offer the dark, moist environment that these fungi crave. Think under boat seats, ski lockers, boat covers, hanging lockers, lazarettes, under cockpit seats, chain lockers, and a host of other hidden areas, many of which are barely accessible, if at all.

So, now we know “where mold grows and why” but how do we prevent and protect our boats so mold can’t grow? Is there anything I can spray on boat seats to stop mold from growing?

Keeping mold and mildew at bay on a boat is a never-ending battle. Once mold spores land on a moist surface that offers some nutrients, they can begin to colonize. By the time mildew is visible, it can produce enough spores to spread throughout your boat. Preventative measures are the best course of action.

This year we traveled to IBEX 2021 in Tampa, Florida on the hunt to find the most amazing products that we thought would bring value to the Used Pontoon Boats For Sale Community.

What we found was Xanigo. These guys are passionate! And they are on a mission to solve one of the biggest, never-ending battles of owning a boat! Here’s what we learned, and now we can pass the news on to you! Quick tip: Preventing Mold is the Best Defense.

We tested 14 other mold and mildew cleaners, and two household products stood out: the super-chlorinated Klean-Strip Mildew Stain Remover and Spray Nine, a chlorine-free household cleaner. After that test, several readers asked about products to prevent mold. One product in particular, Concrobium Mold Control, was repeatedly suggested for testing.

We found Concrobium at Home Depot, and to make things interesting, we included two other mildew preventers that readers suggested: 3M Marine Mildew Block, a treatment formulated to follow the 3M Mildew Cleaner tested in January, and Mold Off, a product billed as an eco-friendly commercial-grade cleaner and protectant at around 30 days..

The final test was Xanigo. Hands down, wow. What if a non-evasive, 90 day re-application process with the top spray atomizer on the market for even spray and easy-to-apply process, was enough to keep your boat looking new and mold free forever. 

How We Tested

Rarely does a boater start to aggressively attack mold or mildew until it becomes a problem. For this reason, we decided to conduct a real-world test on materials that had already been contaminated with mold or mildew. First, the two products that were advertised as both protectants and mildew cleaning agents-Concrobium and Mold Off-were used to clean sections of a mildew-stained life jacket. Cleaning ability was compared to that of Klean Strip Mildew Stain Remover, which was also used on the jacket.

Next, each product was tested for its ability to keep mold from returning. Each product was applied to taped-off sections on two life jackets and three padded, vinyl berth cushions, for a total of five test panels for each product. All surfaces were cleaned and prepared as directed, and the prep and application process was repeated three times over the course of five months. For control purposes, sections were left untreated on each of the test items.

One PFD was stored in a dry locker on our test powerboat, the other in the typically damp underseat locker of a Bennington Pontoon Boat. The vinyl cushions were kept in the humid cabin of our test powerboat. Temperatures during the test period ranged from 30 to 80 degrees, and humidity was usually above the threshold for mold growth (about 60 percent). The life jackets were not used during the test.


The system consists of a highly effective, anti-microbial that remains on the surface and active for 90 days stopping single cell organisms cold in their tracks. Along with a powerful applicator that makes short time of the task to protect your marine materials from mold and mildew which plaques boat owners. The system is proven and the anti-microbial is highly recognized by the boating industry's #1 Pontoon Boating Community, Used Pontoon Boats For Sale. 


Literally a 5 - 10 minute job a few times a season saves hours of scrubbing seat vinyl, life jackets, Bimini tops or any area where mold and mildew tends to grow on your boat. 

Keep your boat's resale value intact by not allowing your interior to fall victim to mold and mildew. Also, save significant costs in time or money by eliminating heavy cleaning or detailing. 

Xanigo is an effective and ready-to-use disinfectant. Hypochlorous Acid HOCl) is a naturally occurring ingredient known for its powerful yet cleaning properties. HOCl has been shown to clean without the harmful effects. Our hospital grade 200 ppm all purpose cleaner is proven to have the longest shelf life of its kind and is Made in the USA.


Left to right: 3M Marine Mildew Block; Mold Off; Klean Strip Mildew Stain Remover; Concrobrium Mold Control

Concrobium Mold Control

The Concrobium purportedly works by forming a physical barrier over the mold, which crushes the mold spores and kills them. This also forms a protective layer to which mold cannot attach and grow. It can be applied to a variety of surfaces, including fabrics and wood, without staining, although the maker advises testing on a small area first.

To apply inside a large boat being put into storage, a fogger is the most effective means of application. Foggers can be rented at Home Depot stores for $25 per day. The fogger applies the Concrobium in a fine mist that penetrates hard-to-reach areas. The Concrobium must dry in order to work properly. Pre-cleaning with bleach will inhibit performance, so any surfaces that have been cleaned with bleach must be well rinsed and dried before applying Concrobium.

In our testing, the Concrobium was not a great cleaner. Difficult stains will require scrubbing and you must let the Concrobium dry to do its work. We left it on the life jacket overnight before cleaning with a soft brush. It cleaned minor stains with scrubbing, but on tough stains, it did not match the fast-acting cleaning of the Klean Strip.

As a protectant, it was somewhat effective against mildew on all the tested surfaces. The bottle calls for reapplication on a weekly basis, although one of the vinyl panels of our test panels showed no noticeable growth at 30 days. On one cushion that got wet, mold did return, as it did for every protectant on that same cushion, except for Xanigo.

Bottom line: Concrobium could be used as part of a mold-prevention strategy. It is not a cure-all, and will need to be applied regularly to products that see a lot of moisture or abrasion, like seat cushions, and will need to be re-applied regularly. 

Mold Off

Mold Off is advertised as an environmentally friendly commercial cleaner that is available to the public for home use. It is not registered as a fungicide with the EPA. Available in 32-ounce spray bottles or gallon jugs in concentrated form, it can be diluted with water. It contains no chlorine or bleach and has a neutral pH balance.

It is advertised as a mold and mildew stain remover, but it also claims to prevent the recurrence of mold and mildew for several weeks. The maker says it can be safely used on canvas, sails, vinyl seats, carpet, and other materials. For soiled surfaces, the maker advises applying it in the sunlight, allowing it to dry overnight and then wiping off. Another coat is supposed to be applied but not wiped off.

We tested Mold Off full strength and diluted. It worked moderately well as an overnight cleaner, better than the Concrobium, but not nearly as effective as the Klean Strip. It held growth at bay on all surfaces for three weeks, when the Javelin-stored life jacket, and two vinyl panels began to show some mold growing again.

Bottom line: Mold Off protection seemed to wear off faster than Concrobium, and it is more expensive. We plan to do more controlled experiments with the Mold Off on various surfaces.

3M Marine Mildew Block

Designed as the second step of a two-step mildew cleaning and treatment, 3M Marine Mildew Block comes in a 16-ounce spray bottle and is advertised as safe for most marine surfaces. The product is not registered as a fungicide with the EPA. Like most mildew protectants, this product claims to lay down an invisible film to prohibit mold and mildew from growing.

As a protectant, the Mildew Block did well, although the spray applicator dribbled more than the Concrobium or Mold-Off. It did not do as well on the bow-locker-stored life jacket, and one of the vinyl cushion panels began to show mold along one edge after about 10 days. Since this is where the edge of a cushion met a bulkhead, the protective layer may have rubbed off during use.

Bottom line: This product appears to work as directed, but it is expensive compared to Concrobium and has more precautions concerning use.

Xanigo & Goldshield

Goldshield is an anti-microbial that provides long-term protection. Because it's positively charged, it has better adhesion to surfaces and sprays consistently with the Xanigo Atomizer. It is a water-based, ready-to-use, liquid spray that is effective against microbes on virtually any surface and most textiles. One easy application delivers on-going protection for weeks or months. On top of that, the Freedom and Defender, SPEED UP DISINFECTING PROCESS WITH A DISINFECTANT SPRAYER The Xanigo disinfectant atomizers give you the ability to disinfect a boat of any size in a very short period of time. Of course, they help you calculate the most effective time by taking into consideration the amount of flat surfaces and touch points to be covered, square footage of the space, and the dwell time of the disinfectant being utilized. Depending upon these aspects, they will even suggest the right Xanigo atomizer for the job. Available in both a corded and cordless solution!

Bottom line: This product works better than expected! It is expensive compared to the cheaper solutions but the protection lasts much longer! In some of our tests, mold was prevented for up to 90 days! Easy to use, and no need to reapply often!.


Our field test approach introduced some uncontrolled variables, but we found this approach to be helpful in determining how these products would perform when used in the field.

Because the tests used multiple panels and were repeated three times, we are confident in making a recommendation. It was interesting to note that even the untreated panels of the locker-stored life jacket stayed clean, suggesting that these sprays offer no advantage if preventative measures are taken.

As protectants, all of the products worked as advertised, but the Xanigo was the most consistent. All of the products seemed to be easily rubbed or washed away by use, so life jackets and cushions would likely need frequent treatment.

Ultimately, Xanigo is a safe, economical spray for protecting a boat or equipment that is in storage. On problem boats, one might consider fogging the boat interior prior to winter storage. We still regard active prevention-keeping the boat dry and well-ventilated-as cornerstones of any anti-mildew strategy.