RMR-86 vs Concrobium Mold Control: Which Works Better?

So you’ve got mold. Maybe it’s that black stuff creeping up your shower grout, or maybe you found some nastiness in the basement. Either way, you’re standing in the cleaning aisle staring at two very different bottles: RMR-86 and Concrobium Mold Control.

Here’s the thing—they both work, but they work in completely different ways. And honestly? You might need both.

Let me break this down.

What Are These Things, Anyway?

RMR-86 is basically bleach on steroids. It’s an instant mold stain remover that uses sodium hypochlorite (fancy name for bleach) to absolutely demolish mold stains. You spray it on, wait about 15 seconds, and watch the black stains literally disappear. It’s kind of satisfying, actually.

Concrobium Mold Control is the complete opposite. No bleach, no harsh chemicals, no fumes. It works by crushing the mold spores as it dries—forming a barrier that prevents new mold from growing. It’s more of a “kill it and keep it from coming back” product.

RMR-86 vs Concrobium: Head-to-Head

Feature	RMR-86	Concrobium
Active Ingredient	Sodium hypochlorite (bleach)	Proprietary inorganic salts
Best For	Removing visible black stains	Prevention & light cleaning
Speed	Instant (15-30 seconds)	Takes time (needs to dry)
Fumes	Strong bleach smell	Odorless
Surface Safety	Can damage some materials	Safe on most surfaces
Price (per oz)	~$0.50-0.60	~$0.40-0.50
Kills Mold?	Yes	Yes
Prevents Regrowth?	No	Yes

When to Use RMR-86

Look, if you’ve got black mold stains that make your bathroom look gross, RMR-86 is your weapon. It’s not subtle. It’s not gentle. But it works.

I’m talking about:

Shower grout that’s turned black
Bathroom ceilings with those dark spots
Vinyl siding that’s covered in algae or mold
Anywhere you need those stains gone right now

The RMR-86 instant mold stain remover works faster than anything else I’ve seen. You spray it, count to 15, and the stain just… vanishes. It’s almost weirdly satisfying.

But here’s the catch: it doesn’t prevent the mold from coming back. You’re just removing the stain. The conditions that caused the mold? Still there. So unless you fix your ventilation or moisture problem, you’ll be spraying RMR-86 again in a few months.

Also, ventilate the hell out of wherever you’re using this. The fumes are no joke. And don’t even think about using it on anything delicate—it’ll bleach fabric, damage certain plastics, and can mess up some finishes.

When to Use Concrobium Mold Control

Concrobium is what you use when you want to actually solve a mold problem, not just hide it.

Best uses:

Prevention in basements, crawl spaces, or anywhere prone to mold
After you’ve cleaned with something stronger (like RMR-86)
On porous surfaces like drywall or wood where bleach doesn’t penetrate
Around kids or pets where you don’t want harsh chemicals
When you need something for bathroom mold that won’t gas you out

The thing about Concrobium vs RMR-86 for mold removal is that Concrobium actually penetrates porous surfaces. Bleach-based products like RMR-86 mostly just sit on the surface. If you’ve got mold growing in drywall or wood, Concrobium is the better choice.

Plus, it creates a protective barrier as it dries. So it’s actually preventing new mold from growing in that spot. That’s huge if you’re dealing with a chronically damp area.

Is Concrobium better than RMR-86 for everything? No. It won’t remove heavy stains as fast. But for actual mold control? Yeah, it’s better.

Price: Which is Cheaper?

They’re pretty close, honestly.

RMR-86 runs about $15-20 for a 32oz bottle. Concrobium is usually $12-18 for the same size, though you can get bigger jugs if you’re treating a larger area.

Per ounce, Concrobium is slightly cheaper. But here’s the real question: what are you actually trying to accomplish?

If you need to quickly clean something before showing your house or having guests over, the extra couple bucks for RMR-86 might be worth it for the instant results. If you’re trying to keep your basement from turning into a science experiment, Concrobium is the better long-term investment.

So Which is Better: RMR-86 or Concrobium?

Here’s my honest take: they’re tools for different jobs.

Choose RMR-86 if:

You need instant stain removal
You’re dealing with tough black mold stains on non-porous surfaces
Speed matters more than prevention
You can handle strong fumes and you’ve got good ventilation

Choose Concrobium if:

You want to prevent mold from coming back
You’re treating porous surfaces like drywall or wood
You need something non-toxic (kids, pets, or sensitive spaces)
You’re willing to wait for it to work

The real answer? Use both. Hit the stains with RMR-86, let it do its magic, rinse it off, then follow up with Concrobium to prevent the mold from growing back. That’s what the pros do.

I’ve seen people argue online about which is better—RMR-86 or Concrobium for bathroom mold, which works faster, which actually kills the mold. But they’re asking the wrong question. It’s not about which is “better.” It’s about using the right tool for what you’re trying to fix.

Got a moldy shower that looks disgusting? Start with RMR-86. Got a damp basement that keeps growing mold no matter what you do? That’s a Concrobium situation.

And honestly? If you’ve got a serious mold problem—like more than a few square feet, or if it keeps coming back, or if you’re seeing it in multiple places—neither of these is your real solution. You’ve got a moisture problem, and these are just band-aids. Get a dehumidifier. Fix your ventilation. Find the leak.

But for everyday mold control? Yeah, keep both of these under your sink. They’re cheap insurance against gross bathrooms and musty basements.

Frequently Asked Questions

Can you use RMR-86 and Concrobium together?

Yes, and that’s actually the best approach. Use RMR-86 first to remove visible black mold stains, rinse it off completely, then apply Concrobium to prevent the mold from growing back. This one-two punch gives you both instant stain removal and long-term prevention.

Is RMR-86 better than bleach for mold?

RMR-86 is essentially a stronger, more concentrated form of bleach (sodium hypochlorite). It works faster than regular household bleach—usually in 15-30 seconds compared to several minutes with bleach. However, it has the same limitations: it only removes surface stains and doesn’t prevent regrowth.

Does Concrobium actually kill mold or just prevent it?

Concrobium both kills existing mold and prevents new growth. As it dries, it crushes mold spores and forms a protective barrier on the surface. Unlike bleach-based products, it penetrates porous surfaces like drywall and wood, killing mold beneath the surface.

Which is safer to use around kids and pets – RMR-86 or Concrobium?

Concrobium is significantly safer. It’s non-toxic, has no harsh fumes, and doesn’t require ventilation. RMR-86 contains bleach, produces strong fumes, and requires good ventilation and protective gear. Always keep both products out of reach of children and pets during use.

How long does Concrobium take to work compared to RMR-86?

RMR-86 works almost instantly—you’ll see stains disappear in 15-30 seconds. Concrobium takes longer because it needs to dry completely to form its protective barrier, usually 2-3 hours depending on humidity. For immediate visual results, RMR-86 wins. For actual mold elimination and prevention, Concrobium is more thorough.

Can I use RMR-86 on grout?

Yes, RMR-86 works great on grout for removing black mold stains. However, because grout is porous, the bleach only treats the surface. For better long-term results on grout, clean with RMR-86 first, then follow up with Concrobium to penetrate and prevent mold from growing back inside the grout.

Will Concrobium remove black mold stains?

Concrobium will kill the mold but won’t necessarily remove heavy black stains as quickly as RMR-86. For light discoloration, Concrobium can work over time. For heavy black stains, you’ll need a bleach-based product like RMR-86 first, then use Concrobium for prevention.

Do I need to rinse RMR-86 off?

Yes, you should rinse RMR-86 off surfaces after the stains are gone, especially if you plan to apply Concrobium afterward. The bleach residue can interfere with other products and continue to off-gas fumes. Use clean water and wipe or rinse thoroughly.

Which product is better for basement mold – RMR-86 or Concrobium?

For basements, Concrobium is usually the better choice because basement mold is often a recurring moisture problem. Concrobium penetrates porous surfaces like concrete and wood, and its preventive barrier helps in high-humidity environments. Use RMR-86 only if you have heavy visible staining to remove first.

Is RMR-86 safe on all surfaces?

RMR-86 can damage or discolor fabric, carpets, certain plastics, and some finishes. Always test on an inconspicuous area first. It’s safe on most hard, non-porous surfaces like tile, vinyl siding, and porcelain when used according to directions. Concrobium is safer on a wider variety of surfaces.