Finding an effective algae killer for concrete can be challenging, especially for broad outdoor surfaces like driveways, patios, and sidewalks. The following selections are popular, ready-to-use or easy-to-dilute formulas designed to remove green and black stains from algae, moss, and mildew without heavy scrubbing or power washing. This guide highlights five reliably effective options and offers practical buying guidance to help you compare formulations, application methods, and maintenance expectations.
| Product | Type | Surface Coverage Notes | Application Style |
|---|---|---|---|
| Wet & Forget Ready To Use Outdoor Cleaner (64 oz) | Ready-to-use spray | Multi-surface; dries to reveal cleaner surfaces over weeks | Spray on dry surface; no rinse; rain and wind aid cleaning |
| Wet & Forget Concentrate Outdoor Cleaner (128 oz) | Concentrate for dilution | Suitable for driveways, patios, roofs, siding, and more | Mix with water; spray dry surface; no rinse |
| Wet & Forget Outdoor Moss, Mildew, Algae Stain Remover (Xtreme Reach, 48 oz) | Hose-end cleaner | Ideal for roofs, siding, driveways; long-range nozzle | Attach to hose; spray from a distance; no rinse |
| 30 SECONDS Outdoor Cleaner (2 pack) with Hose End Sprayer | Hose-end cleaner, two-pack | Vinyl siding, deck, patio, brick, and more | Spray on; hose off; easy hose-end operation |
| Mold Armor E-Z House Wash (64 oz) | Siding and surface cleaner | Bricks, concrete, trim, siding and more | Spray-on application; hose-end adapter; rinse optional |
Note: This table provides a quick comparison of formats and typical use cases. Always follow label directions and test a small area before broad application.
Wet & Forget Ready To Use Outdoor Cleaner
Product: Wet & Forget Ready To Use Outdoor Cleaner (64 oz) is a ready-to-apply formula designed to tackle green and black stains caused by algae, moss, mold, and mildew on multiple surfaces including concrete. Application uses a high-capacity trigger sprayer for targeted cleaning. The product requires no scrubbing, rinsing, or pressure washing; it relies on rainfall and surface wind to help with cleaning over time. For best results, apply to a dry surface on a cool day and avoid rain within 4–5 hours. Surfaces can stay clean for up to a year or longer, though older stains may take several months to fully vanish.
Key features include: ready-to-use spray nozzle, no scrubbing, no rinsing, multi-surface compatibility, and long-term cleanliness with spacing for weather-assisted cleaning. It’s suitable for porches, headstones, fountains, planters, canvas, upholstery, and concrete.
Wet & Forget Concentrate Outdoor Cleaner
Product: Wet & Forget Concentrate Outdoor Cleaner (128 fl. oz.) is a dilute-to-use concentrate designed to remove green and black stains from moss, mold, mildew, and algae across a variety of surfaces including concrete, vinyl, wood, and upholstery. The application method is simple: mix 1 part Wet & Forget with 5 parts water in a garden sprayer, spray the surface, and let it dry. Do not rinse. Plan for cleaning to progress over time, with rain and wind aiding the process. Avoid application if rain is forecast within 4–5 hours and apply on surfaces above 32°F (0°C).
Wet & Forget Outdoor Moss, Mildew, Algae Stain Remover (Xtreme Reach)
Product: Wet & Forget Outdoor Moss, Mildew, Algae Stain Remover with Xtreme Reach Hose End (48 fl. oz.) features a new nozzle designed for extended reach. It attaches to a garden hose and can spray up to 30 feet, enabling convenient treatment of roofs, siding, driveways, and decks. Like other Wet & Forget products, it requires no scrubbing or rinsing and should be applied to a dry surface on a cool day. Allow time for the solution to work, with green stains generally fading within 1–2 weeks and heavier stains possibly taking several months. Clean surfaces can remain stain-free for up to a year or longer.
30 SECONDS Outdoor Cleaner (2 Pack)
Product: 30 SECONDS Outdoor Cleaner (2-pack) with hose-end sprayer cleans stains from algae, mold, mildew, and moss on vinyl siding, decks, patios, brick, and more. It is safe for lawns and plants when used as directed. The spray-on formula makes application easy and then hoses off. It is designed to deliver quick action without the need for pressure washing, with the convenience of a hose-end sprayer for broad areas.
Mold Armor E-Z House Wash (64 oz)
Product: Mold Armor E-Z House Wash (64 oz) kills mold and mildew while cleaning siding, brick, concrete, and trim in minutes. It can be used as a refill for hose-end Mold Armor products and covers up to 4,500 sq. ft. The formulation includes foaming action to lift dirt and stains, with Microban technology aiding longer-lasting cleanliness. Suitable for vinyl siding, brick, stucco, aluminum, wood trim, PVC, and other common exterior materials. No heavy scrubbing required; rinse option is available but not mandatory in many scenarios.
Buying Guide: Key Purchase Considerations
- Target surface compatibility: Concrete, brick, siding, roofs, and decks each respond differently to cleaners. Look for products explicitly stated as safe for concrete and masonry to avoid damage or staining.
- Application method: Choose between ready-to-use sprays, concentrates, and hose-end sprayers based on project size, convenience, and storage space.
- Time-to-clean and maintenance: Some formulas deliver results within days, others require weeks or months. Consider how long you’re willing to wait for results and how long surfaces stay clean.
- Environmental and safety considerations: Read label directions for outdoor use, plant safety, and runoff. Many products are designed to be safe around vegetation, but it’s prudent to avoid flushing cleaners into lawns or gardens.
- Stain type and severity: Green stains from algae or black stains from mold may respond differently. For heavily established stains, formulations with longer wind and rain-assisted action may be needed.
- Water pressure and access: Hose-end cleaners are expedient for larger areas but may require stable water pressure and accessible hoses. Ready-to-use options are excellent for spot-cleaning or smaller sections.
- Longevity of results: Some products boast long-lasting cleaning for up to a year or longer, while others focus on rapid, short-term improvement. Consider climate, rainfall, and sun exposure in your area when predicting durability.
- Cost per application: Compare concentration requirements, bottle size, and coverage estimates to determine long-term value for your space.
- Safety and storage: Store in a cool, dry place away from direct sunlight; ensure child- and pet-safety when choosing formulations used around outdoor living spaces.