Welcome to Pool Ownership—Let’s Talk About a Hidden Threat: Black Algae

If you’re a first-time pool owner in Austin, Liberty Hill, Cedar Park, or anywhere near the lakes, you’re in for a fantastic time. A backyard pool is a luxury—a place to relax, entertain, and cool off during the scorching Texas summers. But as a pool cleaning expert, I want to warn you about a common but often misunderstood problem: black algae.

If you’ve never dealt with black algae before, count yourself lucky. It’s one of the hardest pool contaminants to get rid of, and—surprise!—it often comes from the very lakes we love to swim in.

How Does Black Algae Get Into Your Pool?

Austin is surrounded by beautiful lakes—Lake Travis, Lake Austin, Lake Georgetown—and they’re perfect for a weekend escape. But they also harbor bacteria and algae, including black algae, a stubborn, chlorine-resistant organism that thrives in natural water sources.

The biggest way black algae spreads to pools?

🚤 Lake toys, floats, swimsuits, and even people who have been in the lake!

When you take your rafts, pool noodles, or even life jackets into a lake and then bring them back into your pristine, chemically balanced pool, you could be introducing black algae spores—and once they take hold, they are extremely difficult to remove.

What Makes Black Algae So Hard to Kill?

Unlike common green pool algae, black algae burrows deep into your pool’s surfaces, forming stubborn black spots on the walls and floor. It has a protective outer layer, making it resistant to chlorine, and its roots dig into porous surfaces like plaster, making it almost impossible to scrub away completely.

Signs of black algae in your pool:
✅ Black or dark blue-green spots on the walls or floor
✅ A slimy or rough texture on the affected area
✅ Growth that keeps coming back even after brushing

How to Prevent Black Algae from Entering Your Pool

The best way to deal with black algae? Don’t let it in to begin with. Here’s how you can keep your pool safe:

1. Keep Lake & Pool Toys Separate

🚫 DO NOT use the same floats, rafts, or pool noodles in both the lake and your pool.
💡 If you enjoy taking inflatables to Lake Travis, Lake Austin, or Lake Georgetown, have a dedicated set of lake-only floats.

2. Clean & Sanitize Everything That Touches the Lake

If you must use the same floats or toys, sanitize them properly before putting them in your pool.

🧼 How to clean lake gear before putting it in your pool:
1️⃣ Spray everything down with a chlorine-based cleaner or bleach solution.
2️⃣ Scrub surfaces with a pool brush or sponge.
3️⃣ Rinse thoroughly with fresh water and let them dry completely in the sun.

3. Rinse Off After Swimming in the Lake

Before jumping into your pool after a day at the lake, take a quick shower or rinse off with a hose. This removes bacteria, algae spores, and sunscreen residue that could contaminate your pool water.

4. Maintain Proper Pool Chemistry

Keeping your chlorine levels high and your filtration system running efficiently is your best defense. A well-maintained pool is less likely to develop black algae.

How to Get Rid of Black Algae If It’s Already in Your Pool

If you suspect black algae has made its way into your pool, act fast. The longer it sits, the deeper its roots grow.

🔹 Step 1: Brush aggressively with a stiff-bristle algae brush (not a soft pool brush).
🔹 Step 2: Shock your pool with extra-high levels of chlorine (you may need 2-3x the normal shock dose).
🔹 Step 3: Scrub again—black algae has deep roots, so you’ll need to break through its protective layer.
🔹 Step 4: Run your pump continuously for 24-48 hours and backwash or clean your filter.
🔹 Step 5: If it persists, call a professional (like us!).

Final Thoughts from Your Pool Pro

Austin’s lakes are beautiful, and there’s no reason you shouldn’t enjoy them—just be mindful of what you bring back with you. Black algae is preventable, but once it takes hold, it’s a long battle to remove.

If you’re ever unsure about your pool’s water quality or notice suspicious black spots, Blue Ocean Pool Service is here to help. We specialize in preventing and treating black algae, so you can enjoy crystal-clear, hassle-free pool ownership.

📞 Need help? Call us today for a free pool health check!