If you own a pool in Cairns, you’ve likely experienced the “Overnight Green.” You go to bed with a blue pool and wake up to something resembling a swamp. In the tropics, algae isn’t just a nuisance; it’s an opportunistic organism that thrives in our specific backyard conditions. To beat it, you have to stop thinking about “cleaning” and start thinking about “biology.”
Why Cairns is an Algae Super-Incubator
Algae needs three things to bloom: sunlight, warmth, and nutrients (phosphates).
- Warmth: Algae grows faster in warm water. During a Cairns summer, pool temperatures can hit 30°C+, creating a literal petri dish.
- Sunlight: Our high UV levels provide the energy algae needs for photosynthesis.
- Phosphates: This is the “hidden” factor. Phosphates are algae food. They enter your pool via fertilizers, bird droppings, and the organic debris washed in by tropical storms.
Most people make the mistake of just throwing a bag of “shock” in the pool and hoping for the best. To beat it for good, follow this scientific approach:
Step 1: Balance the pH First Chlorine is “lazy” in high pH water. If your pH is above 7.8, your chlorine is only about 20-30% effective. Before you try to kill the algae, bring your pH down to 7.2–7.4. This “unlocks” the power of your sanitizer.
Step 2: Reach “Breakpoint” Chlorination You don’t just need chlorine; you need a massive surge of it. You must add enough chlorine to break down the waste products (chloramines) so that “Free Chlorine” can actually attack the algae cell walls. This is known as the “Breakpoint.” If you don’t add enough, you just irritate the algae without killing it, leading to resistance.
Step 3: Starve the Survivors After the pool is blue again, you likely still have high phosphate levels. If you don’t remove the “food,” the algae will return the moment your chlorine level dips. Use a high-quality phosphate remover to “starve” any remaining spores.
The Role of Filtration
Dead algae is microscopic and turns the water cloudy or milky. This is where your filter earns its keep. In Cairns, we recommend Glass Media over traditional sand. Glass media is finer and can catch smaller particles, meaning you spend less time backwashing and more time swimming.
How to Prevent the "Forever Green"
The secret to an algae-free pool in FNQ is circulation. Stagnant water is where algae starts. Ensure your return jets are pointing in a direction that creates a “vortex,” moving water into the corners and behind the steps.
If you’re struggling with a stubborn bloom, don’t just keep pouring chemicals in blindly. Bring a 1-litre sample of your water into our Manunda or Edmonton shops. Our free digital water testing identifies phosphate levels and mineral imbalances that the naked eye (and basic home kits) can’t see. We’ll give you a step-by-step “prescription” to get your pool back to being the “Clear Choice.”