Black Algae Removal
in Las Vegas
Black algae is the most stubborn and destructive pool algae type. It doesn't float in the water — it roots into your plaster and protects itself with a waxy outer coating that normal chlorine levels cannot penetrate. Standard brushing and shocking won't fix it. It requires a completely different approach.
How to Identify Black Algae
Black algae is misidentified less often than mustard algae — the dark spots are unmistakable once you know what you're looking at. But it is sometimes confused with mineral staining, mold, or general discoloration. The distinction matters because the treatment is completely different from anything else in pool care.
- Small black or dark blue-grey spots on plaster walls, floor, or steps
- Spots have a slightly raised, bumpy texture — not flat staining
- Rough, gritty feel when scratched — the waxy protective coating
- Brushing removes the surface layer but the spot returns within days
- Concentrated in rough or porous plaster areas and in cracks
- Persistent in the same locations despite repeated shock treatments
- Metal staining (copper or manganese) — staining is flat and doesn't have a bumpy texture
- Mold or mildew — surface-level, brushes off completely and doesn't return in the same spots
- Calcium deposits — white or grey-white, not dark, and feel hard and crystalline not rough
- Mustard algae — yellow-tan and dusty, brushes off easily, in shaded areas not embedded in plaster
- Dirt or debris — doesn't have a root structure, removes completely with brushing
Why Black Algae Is the Hardest Algae to Remove
Black algae isn't just more persistent than green or mustard algae — it's biologically engineered to survive in a chlorinated pool environment. Understanding its structure explains exactly why DIY treatment almost always fails and why the correct protocol is non-negotiable.
The Four-Layer Defense System
Black algae protects itself with a multi-layer structure that standard pool treatment can't penetrate without professional intervention.
This is why black algae treatment requires surface abrasion first — to physically break the waxy coating — followed by specialty chemical penetration to the root level. Skipping the abrasion step means chemistry never reaches what it needs to kill.
What Black Algae Does to Your Pool Over Time
Black algae is not just an aesthetic problem. Left untreated, it causes progressive, permanent damage to your plaster surface. The longer it stays, the deeper the roots penetrate — and the more expensive the eventual repair.
Weeks 1–4: Surface Colonization
Visible dark spots appear on walls and floor. Roots are shallow at this stage — the easiest and least expensive time to treat. Most homeowners attempt DIY shock treatment here, which temporarily removes surface cells but leaves roots intact.
Months 1–3: Root Penetration
Roots deepen into plaster pores. Spots spread to adjacent areas. The waxy coating thickens. Treatment is still fully effective at this stage but requires more aggressive abrasion and higher chemical concentrations than early-stage treatment.
Months 3–6: Surface Pitting Begins
Root penetration begins causing visible pitting and roughness in the plaster surface. The texture becomes permanently rough in affected areas. Treatment can still eliminate the algae but cannot reverse surface damage already done.
1+ Year: Structural Plaster Damage
Deep root penetration causes significant plaster damage. At this stage, chemical treatment may eliminate the algae but extensive surface pitting and roughness may require a partial or full resurfacing to restore the pool. A drain and acid wash → is often the most effective reset for severely affected surfaces.
Our Black Algae Removal Process
Black algae removal is not a one-visit fix. It requires multiple service visits over 1–2 weeks, and every step in the sequence builds on the previous one. Skipping any step — particularly surface abrasion or filter sanitation — guarantees the algae returns.
Confirm Identification and Assess Severity
We visually verify it's black algae and not metal staining, mineral deposits, or mustard algae. We assess how widely it has spread, how deeply it has penetrated the plaster, and whether the surface shows signs of pitting. The severity assessment determines the treatment intensity and realistic timeline.
Aggressive Surface Abrasion — Breaking the Waxy Coating
This is the step that makes everything else work. Every black algae spot must be physically scraped and brushed aggressively with a stainless steel brush — not a standard nylon brush — to break through the waxy protective coating. Without this step, chemical treatment cannot penetrate to the root level and the treatment fails. We target every visible spot, cracks in the plaster, and any rough or porous areas where black algae embeds.
Precision Chemical Elevation
With the protective coating physically disrupted, we apply specialty chemical treatment at concentrations calculated to penetrate to root depth. The treatment blend and concentration are based on pool volume, current LSI chemistry, and the severity of infestation. This is not a standard shock dose — it requires specific chemistry at elevated levels that standard weekly service doesn't use.
Spot Treatment of Individual Colonies
In addition to overall chemical elevation, we apply concentrated spot treatment directly to each black algae colony. Direct contact at high concentration reaches the root system in a way that general water treatment cannot. This step is repeated at follow-up visits until all colonies are eliminated.
Filter Cleaning and Full System Sanitation
Black algae fragments dislodged during brushing and treatment enter the filter. A filter holding black algae cells can reintroduce them into treated water — undermining the entire treatment. We clean the filter thoroughly after each treatment visit. See our filter cleaning service →
Follow-Up Visits and Monitoring
Black algae treatment is not complete after one visit. We return for follow-up abrasion and chemical treatment at intervals based on root depth and treatment response. Most cases require 2–3 visits over 1–2 weeks for full eradication. We monitor chemistry between visits and document progress at each follow-up.
Black Algae vs Mustard Algae vs Green Algae
Each algae type has a distinct appearance, location, and treatment protocol. Applying the wrong protocol wastes time and chemicals — and allows the algae to progress.
- Turns water cloudy or opaque green
- Free-floating in the water column
- Responds to standard shock
- No surface damage if treated quickly
- Clears in 24–72 hours with proper treatment
- Yellow/tan dusty patches on surfaces
- Shaded, low-circulation areas
- Brushes off but returns quickly
- Spreads via equipment and swimsuits
- Requires targeted elevation + equipment sanitation
- Dark spots embedded in plaster
- Rough, bumpy texture — not flat
- Does not brush off — roots into surface
- Causes permanent plaster damage if untreated
- Requires abrasion + specialty chemistry + multiple visits
Preventing Black Algae From Returning
Black algae doesn't appear out of nowhere — it establishes when specific conditions persist over time. Addressing those conditions through consistent weekly care is the most effective long-term prevention.
- Weekly brushing with a stainless steel brush in rough plaster areas, cracks, and any spot that previously had black algae — this disrupts early-stage colonies before they establish deep roots
- Maintain consistent sanitizer and stabilizer levels so chlorine never drops below the threshold that allows black algae to establish
- Address rough or damaged plaster — porous and pitted surfaces give black algae the foothold it needs; resurfacing deteriorated plaster removes the habitat
- Improve water circulation to eliminate dead zones where sanitizer concentration is lowest — particularly in pool features, spas, and around in-floor cleaning system areas
- Treat phosphate spikes after storms — high phosphates support all algae types including black algae
- Schedule consistent weekly professional service — stable chemistry and regular brushing catch black algae in its early surface-level stage before roots penetrate deep
What Our Clients Say
"Well, it only took me 50 years' of living in the same house with a pool to maintain for all of that time , to finally find a pool maintenance company that actually does what they say they're going to do and what you are paying them to do! I can't tell you how many pool maintenance companies I have had over all that time and none of them ever lasted more than maybe 2 months? why?- Because they never do what they say they're going to do at the time when you first hire them! They might do it for the first month but then they would do less and less maintenance in the subsequent months. I would get so frustrated, hiring a new company one month, only to fire them a month or two later! I developed the attitude if I wanted to have a clean and well-maintained swimming pool , I was going to have to do it myself and that is exactly "