Tulum, Quintana Roo · Mexico
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Water guide

Why a pool turns green in Tulum and how to recover it

A pool in Tulum turns green because of algae, and algae appear when free chlorine drops below 1 ppm, when phosphate in the water exceeds 500 ppb, or when the equipment stopped circulating. In Tulum's climate the full process takes between 24 and 48 hours.

The three causes, and how to know which is yours

CauseHow it looksThe test that confirms it
Chlorine exhaustedEvenly green throughout, no strong smellFree chlorine below 1 ppm
High phosphateTurns green again within days even after you chlorinatedPhosphate above 500 ppb
Equipment failureGreen only in corners, steps or one sideGauge out of range or pump with no flow

Why it happens so fast specifically in Tulum

Three local conditions stack up. Caribbean radiation degrades unstabilized chlorine within hours. The average water temperature hovers around 30 °C, and above that mark algae reproduce much faster. And the surrounding jungle contributes leaves and pollen, which release phosphate as they decompose: algae food. On the highlands a neglected pool holds for weeks; here, two days.

How long recovery takes

Between 2 and 4 days in most cases, without draining the water. Draining a pool in Tulum is a bad idea for two reasons: water costs money and, with the water table this high, an empty pool can suffer hydrostatic uplift and pop out of the ground. The correct treatment is shock, brushing, flocculant, continuous filtering and vacuuming.

What you can do today

  • Check that the pump starts and the gauge is in range. Without circulation no treatment works.
  • Brush walls, steps and corners. Attached algae are protected by biofilm and the chlorine in the water can't reach them.
  • Measure pH before chlorinating. At pH 8.0 chlorine works at less than half strength.
  • Don't drain the pool.

Mistakes that make it worse

  • Adding chlorine without brushing. Attached algae survive and recolonize within two days.
  • Chlorinating at high pH. You spend product with no real disinfecting effect.
  • Ignoring phosphate. If that's the cause, you can chlorinate indefinitely and it will always come back.
  • Turning off the pump to "save electricity". It's the fastest way to lose the water.

Rather we handled it?

We provide weekly maintenance across the 25 areas of Tulum and the Riviera Maya from $1,500 MXN/month, chemicals included and crystal-clear water guaranteed. Message us on WhatsApp with a photo of your pool.

Frequently asked questions

Frequently asked.

How long does it take for a pool to turn green in Tulum?

Between 24 and 48 hours if free chlorine runs out, because of the Caribbean heat and radiation. In areas with jungle around it can be even faster, because phosphate from the leaves accelerates algae growth.

Do you have to drain the pool to clear the green?

No, and it isn't advisable. A green pool is recovered with shock, brushing, flocculant and continuous filtering in 2 to 4 days. Draining it in Tulum is risky: with the water table this high, an empty pool can be pushed up by hydrostatic pressure.

How much does it cost to recover a green pool in Tulum?

From $2,500 MXN depending on volume and how long it's been neglected, including chemicals, brushing, filtering and vacuuming until it's crystal clear.

Keep reading

More water guides.

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