Updated August 2026 · Price and specs checked on amazon.com 2 August 2026

Moldex Mold & Mildew Surface Stain Cleaner with Bleach Review

At $0.28 per fluid ounce this is the cheapest thing on this site by a wide margin, from a manufacturer everyone has heard of, and honest enough to put the word bleach in the product name rather than hiding it behind enzyme language the way two of our gels do. Those are real points in its favor and we are not going to bury them.

The rating is not what it looks like

Moldex shows 4.6 stars. That is the highest average on this entire site, above the 4.4 of the 30 SECONDS spray and well above the 4.2 of our top pick. If we ranked on star average, this would be number one.

That 4.6 rests on 51 ratings. Every other product we cover has between 3,900 and 6,100. The listing has only existed since February 2026.

This is the single most common way product roundups mislead people, and it is worth being blunt about. A 4.6 from 51 people is a weaker signal than a 4.2 from 6,148, not a stronger one. Fifty-one reviews is small enough that a handful of early enthusiasts, or a normal run of luck, moves the number several tenths. It is not evidence of a better product. It is an absence of evidence either way, wearing a high number.

What people are actually cleaning with it

Read the reviews rather than the average and a clear pattern appears. Deck pickets covered in green algae. House siding and a garage. A clay pot going mossy. The north side of a garage wall. Almost every substantive review is outdoors.

There is very little in there about bathroom silicone, which is the job this site exists to solve. One owner notes plainly that it works well but does not shift deep stains, which is exactly what you would expect from a thin bleach spray meeting pigment that has penetrated below a surface.

So we are not going to present this as a like-for-like maintenance product for shower caulk just because it is cheap and it is a spray. What it is, on the evidence available, is a low-cost high-volume bleach spray that does well on broad outdoor surfaces.

Where it genuinely earns its place

Exterior work, where the surface area is large, the cost per ounce is the binding constraint, and nobody cares about a few minutes of dwell. Siding, fences, decks, concrete, painted masonry, the shaded side of a garage. One owner sprayed algae on deck pickets ahead of rain and let the rain do the rinsing, which is a perfectly sensible way to use a $9 bottle.

Indoors, it is a reasonable choice for a large, flat, non-precious surface where you would otherwise be paying three times as much for the 30 SECONDS. For anything where the finish matters, or where the stain has soaked in, spend the extra.

Before you order

It is non-returnable. Hazardous materials transport rules apply, so if it does not work for you, Amazon's usual returns are not the fallback. At $8.99 that is a small risk, but it is worth knowing rather than discovering.

And it is bleach, with everything that implies. Ventilate, gloves, no mixing with anything, and be careful around planting if you are spraying a deck or fence. Our bleach safety guide covers the combinations that are actually dangerous.

Verdict