A swimming pond combines natural bathing with a vibrant ecosystem in your own garden – completely without chlorine or expensive chemicals. However, precisely because a swimming pond relies on biological self-cleaning, managing evaporation, algae growth, and pollution is a constant challenge. For over 60 years, Euro-Matic has been developing technical cover spheres that address this very issue: They reduce water evaporation, slow down light penetration and thus algae growth, and keep out coarse dirt – all without a mechanical cover, which is often impractical for a naturally designed swimming pond.

Why evaporation is an underestimated problem in swimming ponds

Depending on its size, temperature, and wind exposure, an open swimming pond loses significant amounts of water daily through evaporation – in large ponds, this can amount to several hundred liters per day. This not only means a higher need for refilling, but also, if rainwater is used, a faster depletion of the stored reserves. Additionally, with each liter that evaporates, the concentration of dissolved minerals in the water does not decrease proportionally – on the contrary, dissolved substances such as nutrients for algae remain and become more concentrated, while pure water escapes. Reducing the surface area exposed to evaporation therefore has a twofold effect: less water loss and a more stable biological balance.

How floating cover balls work

Floating plastic cover spheres settle tightly on the water's surface, forming a flexible, self-adjusting layer. Unlike a rigid cover, the spheres follow every movement of the water level and adapt to irregularly shaped pond edges, typical of naturally designed swimming ponds. The spheres noticeably reduce the exposed water surface area through which evaporation occurs, while simultaneously blocking some of the incoming sunlight. This inhibits algae growth without affecting water quality through chemicals. Fallen leaves and coarse debris largely remain on the surface of the spheres instead of sinking directly into the water, making cleaning easier.

Material quality: What matters when choosing cover balls

Not every plastic sphere is suitable for permanent use in and around water. UV resistance is crucial to prevent the spheres from becoming brittle or fading over years in direct sunlight, as is the choice of material itself. Depending on the application, Euro-Matic uses either polypropylene (PP) or high-density polyethylene (HDPE) – both materials are weather-resistant, frost-proof, and do not release any pollutants into the water. For recreational applications, such as swimming ponds, it is also important that the spheres remain buoyant even after years of exposure to the elements and do not become waterlogged.

Cover balls compared to other solutions

• Tarpaulin: It effectively reduces evaporation, but is difficult to install in irregularly shaped ponds and must be regularly removed and reinstalled during use.
• Floating cover balls: They adapt automatically, remain permanently on the water and hardly hinder the use of the swimming pond, as they can simply be pushed aside while swimming.
• No cover: Maximum evaporation, increased light exposure and therefore a higher risk of algae growth, as well as more leaf and dirt ingress.

The ease of use is a key factor in favor of pool cover balls in practice: they don't need to be painstakingly removed before bathing, but simply float to the side and back again.

Areas of application beyond the swimming pond

The same technology used to reduce evaporation in private swimming ponds is employed by Euro-Matic across various industries: in fire ponds, industrial water management, wastewater treatment plant basins, and open-air swimming pools. Wherever a large water surface needs protection from evaporation, pollution, or unwanted light penetration, cover spheres offer a low-maintenance alternative to rigid covers. For recreational swimming pond owners, this means they benefit from a technology that has already proven itself in significantly more demanding industrial applications.

Practical advice on dimensioning

For effective evaporation protection, the water surface should be covered as completely as possible with spheres – partial coverage reduces the effect proportionally. The order quantity depends on the sphere size and the area to be covered: smaller spheres adapt better to edges and borders, while larger spheres are more economical for large, open water surfaces. Euro-Matic provides individual consultations to swimming pond operators regarding the appropriate sphere size and quantity, tailored to the pond's shape and size.

Installation and care

The major advantage of cover spheres over fixed cover systems lies in their ease of use: they are simply placed loosely on the water's surface and adjust themselves automatically; no complex installation or permanent anchoring is necessary. Maintenance typically requires only occasional visual inspection, especially after strong winds or autumn leaf fall, to determine if spheres have accumulated in a particular area along the shoreline and need to be redistributed. Because high-quality spheres are made of UV-stabilized polypropylene or polyethylene, they can be expected to last for several years without becoming brittle or discoloring impairing their function.

Frequently asked questions from swimming pond owners

Do the spheres interfere with swimming? In practice, cover spheres can simply be pushed aside when entering the swimming pond and float back into the open area on their own after swimming, so that the covering effect is maintained.

Do the spheres affect water quality? High-quality cover spheres made of food-grade or at least pollutant-free plastic do not release any plasticizers or other substances into the water and are therefore also suitable for swimming ponds where chemical additives are deliberately avoided.

How many spheres are needed? The required quantity depends on the water surface area and the desired degree of coverage; for an almost complete reduction in evaporation, the surface should be largely covered with spheres.

Conclusion

A swimming pond thrives on its natural balance – and this is precisely what floating cover spheres can support, without resorting to chemicals or rigid covers. Less evaporation, less algae growth, and less leaf litter while maintaining full usability: this makes cover spheres a practical addition to any naturally designed swimming pond. Euro-Matic has been manufacturing technical cover spheres for water management and recreational applications for over 60 years. Contact us and let us advise you on the right solution for your swimming pond.