Porous stone surfaces, such as limestone, sandstone, and travertine, are prone to biological growth like algae, mold, and lichen due to their absorbent nature. To maintain their beauty and longevity, follow these proven methods:

1. Regular Cleaning: Use a mild, pH-neutral cleaner and a soft brush to remove dirt and organic matter before biological growth takes hold. Avoid harsh chemicals that can damage the stone.

2. Proper Sealing: Apply a high-quality penetrating sealer designed for porous stone. This creates a protective barrier, reducing moisture absorption and inhibiting biological growth. Reapply as recommended by the manufacturer.

3. Control Moisture: Ensure proper drainage and ventilation around stone surfaces. Fix leaks promptly and avoid letting water pool on the stone for extended periods.

4. Natural Remedies: For light growth, use a solution of white vinegar and water (1:1 ratio) or hydrogen peroxide. Spray, let sit for 10 minutes, then scrub gently and rinse thoroughly.

5. Preventative Maintenance: Trim nearby vegetation to improve airflow and sunlight exposure, which naturally discourages biological growth.

6. Professional Restoration: For severe cases, consult stone care professionals who can use specialized techniques without harming the stone's integrity.

By implementing these strategies, you can effectively prevent biological growth while preserving the natural beauty of your porous stone surfaces for years to come. Remember that consistent care is key – addressing small issues early prevents larger problems later.