Guppies are a popular freshwater aquarium fish known for their vibrant colors and active behavior. Many aquarium owners wonder if it’s necessary to leave the lights on for guppies at night or if turning the lights off is okay.

This comprehensive article will provide a detailed look at guppies’ light requirements to help you make the best decisions for your fish.

If you’re short on time, here’s a quick answer to your question: Guppies do not require light at night and are fine with the aquarium lights being turned off. While not strictly necessary, providing some moonlight or nighttime lighting can benefit guppies by maintaining their day/night cycle and promoting natural behavior.

Guppies Originate from Tropical Environments with Distinct Day/Night Cycles

Guppies are native to tropical freshwater streams and rivers

Guppies (Poecilia reticulata) originate from tropical and subtropical freshwater environments in South America, the Caribbean, and parts of Africa. Their native habitats are typically streams, rivers, and pools located in rainforest areas.

These aquatic ecosystems have pronounced shifts between daylight and darkness every 24 hours (distinct day/night cycles).

In Venezuela for example, where guppies thrive in abundance, the geographic location close to the equator means the duration of daylight remains quite steady throughout the year at 12 hours. However sunrise and sunset times do vary, falling anywhere between 5:30 AM to 6:30 PM (source).

In the wild, guppies experience pronounced daylight/darkness cycles

The daylight/darkness cycle impacts all aspects of the natural guppy lifestyle from foraging and feeding to mating and predator avoidance. Stream-dwelling guppies are most active when conditions are bright, venturing out to find food, display to females, engage threats, and explore their environments.

As dusk approaches, guppies know to seek protective shelter among plants, rocks or crevices. Here they will settle together in groups overnight to rest until morning light cues them to resume daily rituals.

For wild guppies, nearly 12 hours of darkness passes before sunrise rouses them again for another busy day.

Guppy Day (12 hrs) Guppy Night (12 hrs)
  • Foraging & feeding
  • Mating displays & courtship
  • Predator inspection & avoidance
  • General activity & exploration
  • Settling down at night shelters
  • Resting in groups overnight
  • Guppies Have Adapted to Low-Light Conditions

    Guppies can see well in low light due to eye anatomy

    Guppies are small freshwater fish that originate from streams and rivers in South America. Over time, they have adapted some amazing abilities to thrive in low-light conditions.

    One key adaptation is their eye anatomy. Guppies have large eyes compared to their body size, which allows more light to enter the eye. Their pupils can also dilate widely in dark conditions, further improving light capture.

    Additionally, guppies have a high density of rod photoreceptor cells in their retinas. Rods are extremely sensitive to low light levels, allowing guppies to see well when light is scarce. They also have a reflective layer behind their retinas called the tapetum lucidum.

    This acts like a mirror, bouncing light back through the retina and effectively doubling the light available for vision.

    Research has shown that guppies kept in total darkness for one month maintained excellent visual abilities and fed normally, while other types of fish struggled. Truly, guppies are champions of low-light vision in the aquarium fish world!

    Their color vision adapts to function in low light levels

    Another cool fact about guppies is that their color vision changes based on ambient light levels. In bright light, they see colors normally. But in low light, their color vision shifts to be most sensitive to blues and greens – the colors that transmit best underwater in those conditions.

    This adaptation allows guppies to maintain excellent color discrimination even when light is low.

    Scientists discovered this ability by training guppies to distinguish between colors in high and low light situations. The guppies learned to choose different colors in bright light versus dim light, indicating flexible color vision.

    Such adaptability makes great sense, as guppies encounter a wide range of light levels in their natural habitat. Their color vision flexes to maintain function regardless of conditions!

    Next time you observe guppies in a dim aquarium, remember their eyes are equipped with special low-light adaptations. Vision is crucial for fish survival, and guppies have evolved excellent visual abilities to see well in their native dark and murky rivers.

    With enlarged eyes, dilating pupils, rod-dominated retinas and flexible color vision, guppies can take the darkness in stride!

    Complete Darkness at Night is Not Harmful to Guppies

    Turning aquarium lights off provides a natural nighttime environment

    In the wild, guppies experience a natural day/night cycle with periods of light and darkness. Turning the aquarium lights off at night simulates this natural environment and gives guppies a chance to rest.

    Light pollution from aquarium lights shining 24/7 can disrupt their circadian rhythms and prevent proper sleep. Providing 6-10 hours of darkness each night allows guppies to relax and regenerate, just as they would in nature.

    Total darkness also gives guppies a break from the constant activity and stimulation of a brightly lit tank. The lower light levels offer a peaceful, low-stress environment. With fewer visible distractions at night, guppies are less active and more inclined to calmly school together or rest on tank surfaces.

    This nighttime respite is important for their health and wellbeing.

    Total darkness does not cause stress or health problems in guppies

    Many aquarists worry that suddenly turning off tank lights will be a jarring change that distresses fish. However, research shows that guppies do perfectly fine in total darkness at night. In one study, guppies were observed under light/dark conditions that replicated natural photoperiods.

    The fish showed no signs of stress or impaired health in complete darkness compared to daytime light levels.

    In fact, guppies have natural adaptations that help them thrive in low light. Their eyes adjust to let in more light in dark conditions. Large, mobile irises open wider at night to maximize vision. Guppies also have a tapetum lucidum, a reflective layer in the eye that boosts light capture in dim environments.

    So guppies can still see reasonably well to school, feed, and interact even when the lights go out.

    While moonlights or dim night lights can mimic natural moonlight, they are not necessary for guppies’ health. Guppies have evolved to handle regular cycles of light and total darkness. Keeping tank lights off for a full night period provides a more truly natural rhythm that guppies are well-equipped to handle.

    Moonlight or Low-Level Night Lights Can Benefit Guppies

    Replicates natural moonlight in the wild

    In their natural habitat, guppies experience phases of light and darkness as they have evolved under the moon’s glow. Providing ambient moonlight or a low level of artificial light at night replicates the conditions guppies have adapted to over millions of years.

    This moonlight effect allows them to exhibit ordinary nocturnal behaviors even in captivity.

    Moonlight contains a blue spectrum which contrasts with the orange glow of sunrise and sunset. The phases of the moon provide variance in light levels for fish communities. By using a low-wattage blue LED bulb or strip light, guppy owners can emulate this day-night cycle important for a fish’s biological rhythm.

    Allows guppies to exhibit normal nighttime behaviors

    In the dark, guppies cannot see colors, but they retain vision in black and white to discern objects and motion. Natural or simulated moonlight permits normal activities like interacting socially, foraging along tank surfaces and exploring their environment at night.

    According to aquarists, the ideal night light level is quite low – just enough to allow the observation of guppies while maintaining a contrast with daytime conditions. This night light allows guppies to find shelter to sleep and provides for secure spawning sites.

    Aids transitions between day/night cycle

    Guppies as diurnal creatures require distinct light and dark periods. A moonlight effect eases the day/night transition so guppies do not experience abrupt light changes that could shock their systems. Gradual lighting adjustments prevent stress.

    In the same way, guppies in outdoor ponds or indoor tanks with natural lighting benefit from sunrise/sunset conditions rather than lights suddenly turning on and off. Providing low-level night lights ensures their comfort when transitioning between light and dark.

    This allows their bodies to naturally prepare for rest at night.

    Tips for Providing Light at Night for Guppies

    Use an LED moonlight fixture or strip lighting

    An LED moonlight fixture or LED strip lighting placed along the back or side of the tank is a great option for providing low-level illumination at night for guppies. Blue moonlight LEDs give off a pleasant moonlight glow that won’t disrupt the fish’s circadian rhythms.

    The light intensity is very low but just enough for viewing the fish at night. LEDs use little electricity and last a long time, making them an energy-efficient choice. Place the LED moonlight on a timer to turn on automatically in the evening when the main tank light turns off.

    Place a low-wattage blue LED bulb on a timer

    Another option is to place a small, low-wattage (1-3 watts) blue LED bulb in a gooseneck desk lamp and position it over part of the tank. Use a timer or smart plug to turn the bulb on for set hours in the nighttime after the main light turns off.

    The blue LED bulb will provide a soft glow for viewing the tank and fish at night. Blue light spectrum bulbs are ideal because blue light has less impact on fish sleep cycles. Keep the wattage very low to prevent too much light disruption.

    The gooseneck design lets you position the beam exactly where needed.

    Use floating plants to diffuse light

    Floating aquatic plants can help diffuse light from tank lighting and create shaded areas for fish. Plants like duckweed, frogbit, and water lettuce spread across the water surface with long roots hanging down.

    This helps block and scatter light shining down from above, providing dappled lighting effects. The floating plants help shade fish while still allowing you to see the fish at night according to Smart Aquarium Guide.

    Use floating plants in conjunction with low-level blue moonlight or LED bulbs for a naturalistic moonlight glow.


    In summary, guppies do not require illumination at night and are adapted to function in low-light or completely dark conditions. While not necessary for their health, mimicking natural moonlight can be beneficial by maintaining their day/night cycle.

    When setting up aquarium lighting, focus on providing high quality lighting during the day while letting guppies experience a natural nighttime environment. This will lead to healthy, active fish that exhibit natural behaviors.

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