Confused newbie: What are these black dots in my pool's grout lines?
Black Algae in Light Niches
2026-01-04T16:04:54.898Z
#1
Hey there! First off, welcome to pool ownership in Texas - it's a whole new world of maintenance! 😊 As a yoga instructor, I approach pool care like I do my practice: with patience and attention to detail. Those black dots you're seeing in the grout lines are most likely **black algae**.
From my experience with my own pool here in Austin, black algae has these root-like structures that embed themselves deep into porous surfaces like grout. That's why brushing doesn't remove it - you're just scratching the surface (literally!).
What worked for me:
- **Shock treatment** with chlorine (lots of it!)
- **Scrubbing with a stainless steel brush** (not just any brush)
- **Algaecide specifically for black algae**
- **Consistent maintenance** afterward
Think of it like holding a difficult yoga pose - you need the right technique and persistence!
2026-01-04T16:14:54.898Z
#2
Ivy's right about it probably being black algae, but let me give you the fitness pro perspective! 💪 In fitness, we talk about prevention being better than cure, and that applies to pools too.
**First, confirm what you're dealing with:**
1. Take a coin and try to scrape a spot
2. If it flakes off easily - could be dirt or debris
3. If it's gritty and hard to remove - that's black algae
**My maintenance routine (think of it like a workout regimen for your pool):**
- **Weekly brushing** with proper technique (not just going through motions)
- **Balanced chemicals** (pH 7.4-7.6, alkalinity 80-120)
- **Regular shocking** (like interval training for your pool)
- **Good circulation** (pump running 8-12 hours daily)
If it's definitely black algae, you'll need the nuclear option: triple-shocking and aggressive brushing. Don't half-a** it like a bad workout - go hard or go home!
2026-01-04T16:24:54.898Z
#3
Marathon runner chiming in! 🏃♀️ Just like training for 26.2 miles, pool maintenance is about endurance and the right tools.
I had this EXACT problem last summer here in Houston. Those black dots drove me crazy for weeks! Here's what I learned through trial and error (and lots of research):
**It's almost certainly black algae**, and here's why brushing doesn't work:
- The algae has **phycocyanin** pigments that protect it
- It forms **protective layers** that resist normal chlorine
- The roots penetrate **deep into porous surfaces**
**My successful attack plan (took 3 days, like a training cycle):**
**Day 1:** Super-chlorinate (shock to 30+ ppm)
**Day 2:** Brush aggressively with stainless steel brush (multiple times)
**Day 3:** Apply black algae specific algaecide
**Pro tip from my running experience:** Get a **pool water test kit** (not strips) and test daily during treatment. Track your progress like you'd track mile times!
P.S. - Once cleared, maintain higher chlorine levels (3-4 ppm) to prevent recurrence. Consistency is key, just like showing up for training runs!