Discovering unexpected inhabitants in your swimming pool is a common occurrence for many homeowners. From tiny insects to various forms of organic growth, a pool can inadvertently become a temporary home or a challenging environment for a range of organisms. Understanding what might be swimming in your pool and why can help you manage its cleanliness and maintain a welcoming aquatic space. This guide provides an overview of the common biological presences found in pools and strategies for their identification and management.
Identifying Common Insects and Spiders
Swimming pools frequently attract various insects, with some becoming temporary residents. Mosquito larvae, often called “wrigglers,” are small, slender, dark, worm-like creatures, typically about half an inch long. They are usually found near the water’s surface, where they use a specialized siphon to breathe, wriggling downward if disturbed. These larvae develop into adult mosquitoes in about 7 to 10 days.
Water boatmen are aquatic insects characterized by their brown color and oar-shaped hind legs, which they use for propulsion. Backswimmers, also brownish with dark patches and a skinny build, are notable for swimming upside down and can inflict a painful bite if handled. Both feed on algae and other organic matter, with backswimmers also preying on other water bugs like water boatmen.
Diving beetles, measuring 1 to 1.5 inches, possess an almond-shaped body and are often blackish-green with a distinct yellow border around their thorax and wing cases. These predatory insects store air under their wing cases, allowing them to remain submerged for extended periods. They are strong fliers and are sometimes drawn to pools by lights at night. Spiders, such as wolf spiders or funnel-web spiders, may also accidentally fall into pools, often seeking new habitats or prey.
Amphibians, Reptiles, and Small Wildlife
Larger animal visitors, though less frequent, can also find their way into swimming pools. Frogs and toads, seeking water sources or escaping predators, may fall in and struggle to exit due to the pool’s smooth, vertical sides. Their smooth or warty skin and varying sizes make them recognizable.
Reptiles like garter snakes or small water snakes might enter a pool, often by accident or in search of small prey like frogs. Small mammals such as mice and voles, or even small birds, can also inadvertently tumble into the water. These animals are often seeking water or simply misjudge their footing near the pool’s edge, finding themselves unable to climb out due to the smooth, high edges, leading to exhaustion.
Addressing Algae and Other Organic Growth
Beyond living creatures, various organic growths can give the appearance of “something swimming” in your pool. Green algae is the most common type, manifesting as a slimy film on pool surfaces and causing the water to turn a cloudy green hue. It multiplies rapidly, particularly in warm water with low sanitizer levels.
Yellow or mustard algae appears as a dusty, yellowish or mustard-colored film that clings to pool walls and floors, especially in shaded areas. Unlike green algae, it is not slimy and often resembles pollen or sand, making it challenging to distinguish. This type of algae is resistant to normal chlorine levels and tends to reappear easily if not thoroughly treated.
Black algae forms as dark black or dark blue-green spots on porous surfaces like pool walls and steps. It has deep roots that embed into surfaces and a protective outer layer, making it very resistant to standard chemical treatments. Fine organic matter like pollen can also create a yellowish haze, causing cloudy water and consuming pool sanitizers.
Safe Removal and Prevention Strategies
Safely removing pool invaders and preventing their return involves a multi-faceted approach. For insects and small debris, regular skimming with a fine-mesh net is effective for surface removal. Manual vacuuming can clear any settled eggs or organic matter from the pool floor, and routine brushing of pool walls and floors dislodges grime and algae that attract bugs.
Maintaining proper pool chemical balance is foundational for preventing organic growth and deterring insects. Regular testing of pH, alkalinity, and chlorine levels, ensuring they are within recommended ranges, helps sanitize the water and inhibit algae growth. Shock treatments, involving a high dose of chlorine, are effective for killing existing algae and bugs.
To prevent larger animals from entering, installing pool covers provides a physical barrier, keeping out debris, insects, and wildlife. Safety covers, either mesh or solid, can support significant weight, preventing accidental falls. For animals that do fall in, rescue ramps, sometimes called critter saving devices, offer an escape route. These ramps are typically easy to install and provide a visible means for small creatures to climb out. Landscape modifications, such as trimming overgrown foliage around the pool, can also reduce insect habitats and pathways for animals to access the water.