22/05/2026
Natural sun v Ultraviolet bulbs!
☀️ Sunlight (including UV) feeds algae growth
The sun gives off energy across lots of wavelengths — visible light, heat, and some ultraviolet.
Algae (the tiny green stuff making your pond look like pea soup) uses mainly visible light, especially red and blue wavelengths, for Photosynthesis.
More sunlight = more energy = faster algae growth.
💡 A pond UV clarifier kills floating algae
Your Ultraviolet clarifier uses a very concentrated UV-C light (usually around 254 nm).
This damages the algae cells’ DNA so they can’t reproduce.
The dead algae then clumps together and your filter removes it.
The key difference:
Sun UV = broad natural light that helps algae grow
Pond UV = targeted UV-C “steriliser” that stops algae multiplying
A good way to explain it: “The sun feeds the w**d; the UV clarifier fights the symptom.”
Why ponds still go green:
Too much sunlight ☀️
Nutrients in water (fish waste, leaves, overfeeding) 🍂
Warm water 🌡️
Weak/undersized UV or old bulb 💡
Fun fact: most pond UV bulbs should be changed yearly, even if they still glow—because their UV output drops over time.