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Removing Black & Green Algae Made Easy: A How-To Guide

By Wet & Forget
Algae on window sill

Black and green algae stains can cover your home’s exterior surfaces, leaving a slippery mess. Plus, black algae can cause unsightly dark stains across your home’s roof. Keep reading to find out how green and black algae grows on a variety of outdoor surfaces and how to get rid of algae with Wet & Forget.

What is algae and where does it grow?

Algae are a diverse group of simple organisms. Just like plants, these organisms all go through the process of photosynthesis, using sunlight to make food from carbon dioxide and water. Many types of algae, like the green varieties, are related to plants. Like plants, algae also needs access to lots of water to grow. However, green algae doesn’t have stems, leaves or true roots.

Algae is present in soil, and it sends its spores through the air which the wind is notorious for picking up and depositing onto your roof, deck, driveway, and other places around your home. Algae can grow on multiple surfaces, including your porch, patio, awning, siding, fence, sidewalk, and even on your outdoor furniture.

What’s the difference between black and green algae?
algae on rocks

Algae on a stone water feature before using Wet & Forget. ***

If you have dark streaks on your roof, siding, and other outside areas around your home, they likely caused by a type of black algae called gloeocapsa magma. Gloeocapsa magma is a type of cyanobacterium that can survive cold temperatures, wind and harsh sun. This is because of its dark pigment and tough outer capsule. The dark pigment makes gloeocapsa magma hardy enough to thrive in places that are too sunny for green algae to grow. Black algae is a simple growth that can develop on just about any outdoor surface where there is enough moisture, even in the sunny areas. This dark growth stubbornly attaches to surfaces and can be very difficult to clean. The algae can cause black or gray streaks that seem to run down your roof.

If you have green stains on your deck or siding, it’s probably due to either cholophyta algae “green algae” or a cyanobacterium related to gloeocapsa magma. The green color comes from chlorophyll, which is the same substance that makes plants green. Green algae is a smooth and slimy growth that can show up anywhere there is moisture and partial shade. It thrives in areas with plenty of water and not much direct sunlight, such as north-facing walls. Green algae turns everything it touches a deep green and can make surfaces slippery and dangerous to walk on. If left untreated, green algae can completely take over an area.

***We only recommend using Wet & Forget on water features that do not contain fish.

Does algae damage surfaces?

Algae growth on decks and other walkways will make the surface very slippery. This can cause a hazard for you, your family, and guests. Algae growth on your roof can not only ruin the appearance of your home, but it can also wear on your shingles over time. As the algae builds up, your roof becomes less reflective and will absorb more sunlight. The excess of sunlight can increase the amount of heat your roof absorbs. Unfortunately, this means you can expect an increase in cooling costs. If the algae forms a partnership with fungus, it will develop into lichen, an invasive growth that could cause serious damage to outdoor surfaces.

Find out how to remove lichen on your outdoor surfaces here.

How do I get rid of algae?

Clean green and black algae on siding

You might think that pressure washing is the best way to remove algae. However, the force of the water can cause your shingles to lose their protective granules. Pressure washing can even tear shingles off your roof! Some homeowners also try to get rid of algae by using bleach. Bleach is a caustic chemical that can kill your lawn and plants. It can also rust your downspouts and cause your shingles to shed their protective granules prematurely. Using bleach on algae requires brisk scrubbing and rinsing. This is not only time consuming, but it can increase the wear and tear on your roof.

Pressure washing and bleach aren’t the best options for cleaning green and black algae. Even if you try to remove the algae, it can easily grow back because these cleaning methods don’t effectively attack the full growth. Meaning there are traces of algae left behind, and it can quickly come back.

Wet & Forget Outdoor eliminates algae without any bleach, scrubbing or pressure washing. No matter the type of algae you have covering your outdoor surfaces, Wet & Forget Outdoor will take care of it. It penetrates black algae’s defenses and removes the green algae that can grow on the shaded areas of your roof.

algae on swingset

Green algae on swing-set before using Wet & Forget.

Wet & Forget Outdoor works with the wind and the rain to wash away green and black algae stains over time. When applying, just saturate the area well, and the algae will gradually come off the surface over the next few weeks. Once applied, the Wet & Forget starts working to remove algae on outdoor surfaces and is designed to wash the dead growth off over time with the outdoor elements.

Click here to read about one of our customer’s testimonials on how he used Wet & Forget to remove algae that was growing on his patio.

 

swing-set after using Wet & Forget

Clean swing-set after using Wet & Forget.**

If you have algae that’s leaving dark stains on your roof, clean it easily with Wet & Forget Hose End.  Roof cleaning with Wet & Forget is easy as you can apply it with your feet firmly planted on the ground.  The jet tip nozzle will reach surfaces up to 30′, so you don’t need to use a ladder to get onto your roof. The gentle formula of this roof cleaner will not harm or damage your roofing shingles. The new Wet & Forget Rapid Application Hose End product makes it easy to apply to hard-to-reach areas and high elevations.

For green and black algae on your sidewalk or retaining wall we recommend using the Wet & Outdoor Concentrate. Simply dilute the concentrate using a 1 part Wet & Forget to 5 parts water mixing ratio in your garden pump sprayer and spray it onto your outdoor surface. If the algae growth is on a planter or steps, use Wet & Forget Ready-To-Use for a quick application. Wet & Forget Ready-To-Use is premixed, so all you have to do is attach the trigger sprayer and saturate your algae-coated outdoor surface. Wet & Forget cleans the surface properly, so you’re less likely to see regrowth. Most customers don’t see regrowth for up to a year after their application. If you live in the Northern regions of the United States, you shouldn’t see regrowth for a few years!

**When using Wet & Forget on a swing-set, spray the product onto the surface then rinse the surface with water the following day before use.

Application Tips

For optimal results, apply Wet & Forget on a cool, overcast day to avoid rapid evaporation of the product. When applying the Wet & Forget Concentrate or Wet & Forget Ready-To-Use temperatures should be between 32°F and 80°F while applying and for the next 4 to 5 hours while the product dries. When using Wet & Forget Hose End, temperatures should be between 55°F and 80°F during the application and for the drying period. It’s best to spray algae on a day that’s not too sunny, to prevent the product from evaporating rapidly. Cooler weather ensure that the surface remains wet, and this gives the product time to do its job. It’s important to make sure the Wet & Forget has enough time to work on the surface to effectively remove the algae.

Black algae’s tough outer sheath may cause it to take longer than green algae to disappear completely, so just be patient! When applying Wet & Forget to black algae, you should start to see results 1-2 months after your application. When applying Wet & Forget to green algae, you should start to see results 1-2 weeks after your application. Wet & Forget’s gentle gradual process gets the job done. Once the surface is algae-free, you can use Wet & Forget as maintenance to keep your outdoor surfaces clean. Reapply the product once a year or at the first sight of new growth on the surface.

Don’t waste any more time trying to get rid of algae! Wet & Forget does the hard work for you, so you can and get back to doing the things you love!

Click here to read more about algae and how to remove it from your outdoor surfaces with Wet & Forget Outdoor.

Click here to buy Wet & Forget today, or click here to find it at a store near you.

Stuck with stubborn green algae on your retaining wall? Simply spray Wet & Forget on the surface and walk away! Wet & Forget works with the rain and wind to remove green algae, so you don't have come back and do any scrubbing.