A fountain’s clear, flowing water can quickly turn into an unsightly green pool due to the proliferation of microscopic organisms and mineral deposits. This discoloration is primarily caused by algae, mold, and the concentrated residue of hard water minerals left behind by evaporation. Keeping a water feature pristine requires a strategic, multi-faceted approach that combines regular hands-on cleaning with targeted water treatments. This article focuses on practical, preventative steps to address the biological and chemical issues that cause water to lose its clarity.
Identifying the Sources of Green Water
The green color in fountain water indicates algal growth, which are microorganisms that thrive in specific environmental conditions. Algae use photosynthesis, making prolonged exposure to direct sunlight their primary energy source. Sunlight also raises the water temperature, accelerating their reproductive cycle and allowing populations to double rapidly in warm weather.
The second major contributor is the water’s nutrient load. Organic debris such as fallen leaves, dust, pollen, and bird droppings break down, releasing phosphates and nitrates. These compounds serve as fertilizer, allowing algae to flourish in a nutrient-rich environment.
Poor water circulation also plays a significant role by creating stagnant areas where algae can settle and multiply. If the pump is undersized or partially clogged, the resulting low flow allows organisms to establish themselves on the fountain surfaces. The combination of light, warmth, and organic matter transforms the fountain into an ideal incubator for green growth.
Essential Physical Maintenance and Setup
Long-term clarity begins with rigorous physical maintenance and careful environmental control. Routine scrubbing removes the established biofilm, preventing it from releasing reproductive spores back into the water. This process involves turning off the pump, draining the reservoir, and using a soft-bristle brush or sponge to wipe down all internal surfaces.
For a thorough clean, use a mild, non-toxic solution, such as a 1:1 mixture of white vinegar and water, which helps dissolve mineral deposits and organic slime. After scrubbing, rinse the fountain surface completely to ensure no cleaning residue remains before refilling. Leftover soap or cleaner can alter the water chemistry and promote biological activity.
Pump function is central to maintaining water quality, as continuous movement prevents stagnation and inhibits algae from settling. The pump should be removed and cleaned periodically to ensure the intake screen and impeller are free of debris. Soaking the components in a water and vinegar solution helps dissolve stubborn mineral scale and slime that restrict water flow.
Adjusting the fountain’s exposure to the environment reduces the energy source for algal growth. If possible, reposition the fountain to an area that receives partial shade, especially during the hottest part of the day, to lower the water temperature and limit photosynthesis. If the fountain cannot be moved, adding a shade element, such as an awning or nearby tall foliage, helps deprive the algae of direct sunlight.
Chemical and Biological Water Treatments
Once the fountain is physically clean, adding specific treatments prevents the re-establishment of biological growth. Commercial algaecides are formulated to inhibit or kill algae and often utilize copper-based compounds or organic polymers. Copper-based inhibitors release copper ions into the water, which are toxic to the algae, though caution is advised as these can be harmful to fish or other aquatic life.
Non-toxic treatments, such as organic polymers, function as clarifiers that bind to organic matter and inhibit algal growth without affecting wildlife or plants. These treatments are added in small, measured doses to prevent over-treatment, which can lead to foaming or residue.
Biological controls offer a natural alternative by introducing beneficial bacteria or enzyme treatments. These specialized bacterial blends actively consume and break down the organic nutrients—phosphates and nitrates—that algae rely on for food. Eliminating the algae’s food source naturally suppresses growth, keeping the water clearer.
Another strategy involves using barley straw extract, which releases natural compounds as it decomposes that inhibit algal cell division. Regular water changes are necessary to prevent the concentration of treatment chemicals over time. Replacing the water monthly, particularly during warmer seasons, keeps the water chemistry balanced and the environment less hospitable to new growth.
Managing Mineral Deposits and Scale
A green tint is not always biological, as hard water deposits can also cause discoloration similar to a thin layer of algae. Hard water contains high concentrations of minerals, primarily calcium and magnesium, which are left behind as the water evaporates. This residue forms a white or grayish crusty buildup known as scale, which can sometimes have a greenish or brownish tint from trace minerals like iron.
Scale requires a different treatment approach than algae, focusing on acid-based descalers to chemically break down the mineral bonds. White vinegar is a common and effective household solution, a mild acid that can be scrubbed onto the affected surfaces to dissolve calcium and lime deposits. For heavy accumulation, commercial scale removers containing phosphonates can be added directly to the water to prevent mineral adherence and protect the pump.
Preventing mineral concentration is achieved by limiting the introduction of these minerals. Using distilled or filtered water instead of standard tap water will eliminate a significant source of calcium and magnesium. If using tap water is unavoidable, periodically replacing the entire volume of water, rather than just topping it off, is essential to dilute the mineral levels before they encourage scale formation.