---
title: "What Is Black algae? Pool Glossary | Marina Pool Services"
description: "Black algae shows up as dark spots with deep roots, often in plaster, and needs hard brushing and treatment."
url: https://marinapool.multisites.ai/glossary/black-algae
publisher: Marina Pool Services
phone: +1-817-896-1120
quote: https://marinapool.multisites.ai/contact
---

Water chemistry

# Black algae

Black algae shows up as dark spots with deep roots, often in plaster, and needs hard brushing and treatment.

Black algae is the hardest type to kill. The dark spots grow roots into plaster, grout, and rough surfaces, and a protective layer shields them from chlorine.

Treatment means scrubbing each spot with a stiff stainless steel brush on plaster, then applying chlorine tablets or a targeted product straight onto the spot, and keeping [free chlorine](https://marinapool.multisites.ai/glossary/free-chlorine) high. Avoid steel brushes on vinyl or fiberglass. Spots often return if the roots survive. For stubborn cases, see a pro. Treat [cyanuric acid](https://marinapool.multisites.ai/glossary/cyanuric-acid) and [pH](https://marinapool.multisites.ai/glossary/ph) levels too.

[Marina can helpAlgae Treatment](https://marinapool.multisites.ai/algae-treatment-grapevine-tx)

## Related terms

-   [Green algae](https://marinapool.multisites.ai/glossary/green-algae)
-   [Mustard algae](https://marinapool.multisites.ai/glossary/mustard-algae)
-   [Algaecide](https://marinapool.multisites.ai/glossary/algaecide)
-   [Shock](https://marinapool.multisites.ai/glossary/shock)

## Need a hand with your pool?

Call or text and tell us what your pool needs. Estimates are free for qualifying services, and same-day estimates are possible when the schedule allows.

[Call (817) 896-1120](tel:+1-817-896-1120)[Get a quote](https://marinapool.multisites.ai/contact)

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