How to soft wash red algae stains from render, stone & brick

July 27, 2023

How to soft wash red algae stains from render

We've been asked about the best way to soft wash red algae stains from render, stone and brick walls.

After soft washing, light red algae will go from wall in a few days in warm weather and up to two weeks in winter.

Heavy dark red algae can be problematic as it often has multiple layers of black algae underneath. So be prepared to give multiple softwash treatments.

Benz Bio Cleanze biocide – when used as a stand-alone softwash treatment at up to 20:1 dilution – will clean red algae from wall render in a few months. A second application after a month or so is often advisable to remove any remaining red algae stains.

What if your customer wants the fastest possible results?

The fastest results come from soft washing the worst of the red algae with Benz Lightning Cleanze biocide at 5:1 dilution (go to 4:1 if test results indicate this to be necessary but take care and use full ppe because the softwash solution is getting quite strong at that dilution).

Then follow up with a treatment of Bio Cleanze, after thoroughly rinsing Lightning Cleanze from the wall render, at 40:1 dilution. Bio Cleanze will continue cleaning the red algae through time and impart residual protection against recolonisation.

Click here to learn more about soft washing wall render generally

Click here to learn more about soft washing red algae from wall render specifically

We hope this information is helpful and sincerely wish you great success in your soft washing business,

Benz Team

Click here to get more practical soft washing how-to tips

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "how to" – into our in-site Search Engine (magnifying glass icon on the main menu).

Click here to download our Product Documentation Pack (includes Application & Dilution guides, SDS, PDS, RAMS, PPE & Mask info, COSSH, sample Contract and more)

Order Benz Softwash chemicals & equipment online or by phone:

GB (England, Scotland, Wales)

Phone: 0800 70 74 222 


Ireland and other countries

Phone: 00353 214 622 978


Lines open Monday - Friday, 9am – 5pm

Please note: The above numbers are for orders only (click here for tech support)

PS: Click here to set up your "Clean & Maintain" programme
. After completing an initial soft wash treatment, put your customer on a "Clean & Maintain" ongoing maintenance programme. Your customers will enjoy a permanently clean property and you will enjoy a steady stream of repeat business.

This is clearly a win-win arrangement for you and your customers.


Click here to explore the extensive range of Benz softwash cleaning chemicals & equipment

Benz Softwash Bio Cleanze DDAC biocide & Benz Softwash Lightning Cleanze SH sodium hypochlorite biocide

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