Fountain or water feature: how to keep the water clear, without algae or limescale

A patio fountain often holds less than 50 liters of water, exposed to sunlight, constantly circulating, and evaporating every day. It is a miniature pond with concentrated problems: the water turns green within a week, limescale whitens the stone, and the pump loses power. A fountain stays clear with three things: low-limescale water, regular cleaning of the basin and pump, and a gentle preventive treatment against algae and limescale. Here is the complete method.

Why fountain water turns green so quickly

In a pond, plants, bacteria, and the volume of water buffer fluctuations. In a fountain, none of that is present. The sun heats the few liters of water within a few hours, dust, pollen, and leaves add nutrients, and no plants are there to consume them. Microscopic algae take advantage of the light and multiply: the water turns green, then a green-brown film coats the basin.

Limescale comes from evaporation. Every time you top up the water level with tap water, you add dissolved minerals. The water evaporates, but the minerals remain. After a few weeks, the water in a fountain can be much harder than tap water, and calcium carbonate settles on the stone, nozzles, and pump.

Problems and their solutions

The cleaning routine

1. Unplug the pump before carrying out any work.
2. Empty the fountain. The water can be used to water flower beds unless you have used a product.
3. Brush the basin with a soft brush and water. For limescale deposits, a mixture of water and white vinegar does the job. Rinse thoroughly.
4. Take apart the pump: remove the intake grille or foam filter and rinse it. Take out the rotor and clean it and its housing.
5. Descale if needed: soak scaled-up parts in white vinegar for a few hours, then rinse with clean water.
6. Reassemble and fill, preferably with rainwater.

During the season, plan on a thorough cleaning every two to four weeks, more often in full sun or under trees. Avoid bleach and detergents: they can damage certain stones, leave residues, and birds often come to drink from fountains.

The pump, the heart of the fountain

A fountain pump is a small motor that runs day and night. Two things destroy it: running dry and limescale. Monitor the water level, especially in hot and windy weather, when evaporation and splashing can lower the level by several centimetres per day. If the jet weakens despite a clean foam filter, the rotor is often scaled up or worn. A worn-out pump can be replaced at modest cost, and a pump suited to your fountain's lift height uses less power.

Choosing the right water

Rainwater is ideal: it contains very little limescale and leaves almost no deposits. Collect it in a clean container rather than in a gutter full of moss and debris. If that is not possible, filtered or softened water also helps limit limescale. Tap water is suitable, but replace all the water regularly rather than constantly adding small amounts that concentrate the limescale.

Good installation practices

• Partial shade rather than full sun: fewer algae, less evaporation.
• Away from trees that shed leaves, flowers and pollen.
• A jet suited to the basin: a jet that is too high splashes and empties the fountain in the wind.
• No fish in a small fountain: the volume is far too low.
• Moving water prevents mosquitoes from laying eggs; water that stagnates when the pump is switched off quickly becomes a breeding ground for larvae.

Winter

Frost causes stone, terracotta and concrete basins to crack, and damages pumps. Before the first frosts, empty the fountain, store the pump after cleaning it, ideally in a bucket of water protected from frost so the seals do not dry out, and cover the basin so it does not fill with rainwater.

Read also

For an indoor fountain: How to set up a decorative fountain in your home?

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Frequently asked questions

— How do you clear green water in a fountain?

Empty it, brush the basin, rinse the pump and fill it with rainwater. Then add a preventive treatment for fountains and move it to partial shade if possible.

— Can you put bleach in a fountain?

It is not recommended: it damages certain materials, leaves residue, and birds often drink from fountains.

— How do you remove limescale from a fountain?

With white vinegar, scrubbing the stone and soaking the pump parts, then rinsing thoroughly. Rainwater limits future deposits.

— How often should a fountain be cleaned?

Every two to four weeks during the season, more often in full sun or under trees.

In summary

• Small bodies of water, big problems: sun, nutrients and evaporation explain algae and limescale.
• Rainwater, partial shade and regular complete draining.
• Pump rinsed and descaled with vinegar, never run dry.
• No bleach, a gentle treatment for fountains, and winterization before freezing.

Last updated: September 28, 2026.