Do Molly Fish Need Light? (Everything You Need To Know)

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Molly fish are one of the most common freshwater aquarium fish, and for two main reasons – they are extremely beautiful and easy to care for.

But what about the lighting requirements? Do they need light? And if so, how much and what intensity should you use?

In this article, I will answer all these questions thoroughly, and provide you with my personal recommendation for a lighting system for molly fish.

Let’s get started.

Also Read: Molly Fish Tank Setup

Do Molly Fish Need Light?

Yes, molly fish do require light, but it needs to be properly managed.

They are tropical fish accustomed to a natural day-night cycle, which should be mimicked in an aquarium setting.

This typically involves providing around 8 to 12 hours of light each day, followed by a period of darkness, to best support their biological rhythms and overall health.

Here’s why the right light conditions matter for molly fish:

  • Mimic Natural Habitat: Molly fish originate from tropical regions where they experience regular cycles of day and night. Replicating this pattern in their tank helps maintain their internal biological clocks and promotes natural behaviors.
  • Promotes Healthy Activity: Molly fish are diurnal, meaning they’re active during the day and rest at night. A proper light-dark cycle helps regulate their activity levels and reduces stress, thus improving their overall health.
  • Affects Color Vibrancy: Sufficient light can enhance the vibrant colors of molly fish, making them more attractive and lively. Moreover, light supports the growth of beneficial algae, which not only contributes to the aquarium’s ecosystem but also provides natural color-enhancing nutrients.
  • Temperature Management: Light, particularly from certain types of aquarium lamps, can contribute to maintaining the warm water temperatures that molly fish need (around 25-28 degrees Celsius or 77-82 degrees Fahrenheit).
  • Supports Plant Life: If your molly fish tank contains live plants, appropriate lighting is critical. Aquatic plants rely on light for photosynthesis and in turn, they help maintain water quality, providing oxygen and absorbing excess nutrients, which benefits the mollies.

Also Read: 11 Plants Your Molly Fish Will Love In Their Tank

How Much Light Do Mollies Need?

Molly fish typically require around 8-12 hours of light per day to thrive.

This amount simulates their natural daylight cycle and supports their physiological and behavioral needs.

It’s important to provide a period of darkness, for roughly 12-16 hours, replicating a natural night cycle, which aids in their rest and recovery.

Let’s break down these needs:

  • 8-12 Hours of Daylight: This is the ideal amount of light per day for molly fish. The light does not need to be intense; a regular aquarium light is sufficient. Too much light can lead to algae growth which may disrupt the ecosystem of the aquarium.
  • Adjustable Aquarium Lighting: It’s helpful to have an adjustable light system for the molly fish aquarium. Some molly fish might prefer slightly less or more light than the standard 8-12 hours, so having an adjustable system allows you to adapt to the specific needs of your fish.
  • 12-16 Hours of Darkness: Molly fish require a period of darkness to rest and recover. The period of darkness should ideally match the length of the natural night cycle. Too much continuous light can stress the fish and potentially impact their health.
  • Use of Timers: To ensure the consistency of the light-dark cycle, using a timer for the aquarium light can be a good idea. This automates the process and ensures that the molly fish receive the correct amount of light even if you forget to switch the lights on or off.
  • Avoiding Direct Sunlight: While natural light might seem ideal, placing the molly fish aquarium in direct sunlight can lead to overheating and excessive algae growth. Therefore, it’s best to use controlled aquarium lighting for your molly fish.

Lighting Requirements For Molly Fish

When choosing lights for molly fish, three main factors to consider are the type of light, the light color, and the intensity:

1. LED Lights

Molly fish do exceptionally well under certain lighting conditions, notably with LED lighting. 

LED lights have gained immense popularity in aquarium settings due to their energy-conserving nature and minimal heat generation.

These lights not only highlight the beautiful colors of molly fish but also contribute to a more conducive environment in the tank.

Below are some reasons why LED lights are advantageous for molly fish:

  • Energy Conservation: LED lights are less power-consuming compared to other traditional light sources, making them a cost-effective and environmentally friendly choice for illuminating a molly fish tank over the long haul.
  • Minimal Heat Emission: LED lights are known for their low heat output. This is crucial as high heat from lighting can alter the water temperature, potentially causing stress to the molly fish.
  • Enhanced Color Display: LED lights are recognized for their capability to produce vibrant and accurate colors, hence intensifying the aesthetic appeal of your molly fish and their surroundings.

2. Color Temperature

When selecting lighting for molly fish, color temperature holds significant importance. 

Measured in Kelvin, the color temperature of the light can greatly impact the behavior and health of the fish.

For molly fish, a color temperature mimicking natural daylight (roughly 5000-7000K) is preferred.

Let’s delve into why the color temperature matters:

  • Natural Daylight Imitation: A color temperature within the 5000-7000K range mirrors the natural daylight. This supports the molly fish in maintaining their innate behavior and sleep-wake cycle.
  • Health Promotion: The appropriate color temperature can augment the environment of the molly fish, fostering overall health and wellbeing.
  • Visual Impact on Fish: The color temperature of the light can alter the visual perception of the molly fish’s color. A light spectrum that imitates daylight best brings out their natural colors.

3. Intensity

The intensity of the light is also a significant factor. Molly fish require a moderate light intensity, as too bright or too dim light can stress the fish.

Ideally, the light should provide sufficient illumination for the tank without causing any discomfort to the fish.

The importance of light intensity is further explained below:

  • Comfortable Environment: Moderate light intensity creates a comfortable environment for molly fish, reducing stress and promoting natural behavior.
  • Prevents Algae Overgrowth: Too intense light can promote excessive algae growth. By maintaining moderate light intensity, molly fish owners can keep the algae population in check.
  • Simulates Natural Habitat: Molly fish are not deep-water fish and are used to moderately lit environments. By providing a similar light intensity, you can better mimic the molly fish’s natural habitat.

Setting Up An Optimal Lighting System For Your Molly Fish

When picking the best lighting system for a molly fish tank, my personal recommendation is the Hygger Auto On Off LED Aquarium Light (link to Amazon).

Fortunately, setting it up is pretty straightforward: 

  • Unbox the Product: Carefully remove the Hygger Auto On Off LED Aquarium Light from its packaging. Ensure all parts are included as per the product manual.
  • Position the Light: Place the LED light on top of the aquarium, adjusting the brackets if necessary to fit the width of your tank. The light should cover the length of the tank for even distribution of light.
  • Secure the Light: Secure the LED light onto the tank using the provided screws or clips (if any). Make sure the light is firmly attached and won’t easily fall into the water.
  • Connecting the Light: Simply plug the power adapter into the light and insert it into a nearby power outlet. Ensure the power outlet is safe and far from water to prevent electrical accidents.
  • Set Up Automatic Timing: Program the light to suit your molly fish’s requirements. They typically thrive with 8-12 hours of light exposure. Set the light to turn on in the morning and off in the evening, ensuring a period of darkness to mimic their natural night cycle.

Also Read: Molly Fish Tank Size

Do Molly Fish Need Light At Night?

No, molly fish do not need light at night.

It’s essential to provide them with a period of darkness, replicating their natural day-night cycle, which aids in their rest and overall wellbeing.

Continuous exposure to light can disrupt their natural rhythms and lead to stress, so lights should ideally be turned off during the night.

Do Molly Fish Fry Need Light?

Molly fish fry do require light, although their specific lighting needs may vary slightly compared to adult molly fish:

  • Light Requirement: Much like their adult counterparts, fry necessitate a stable light and dark cycle. However, the light intensity should be softer and not as bright as for adults, since fry are more susceptible.
  • Duration: A daily light cycle of approximately 10-12 hours is generally suggested for fry. This can mimic natural scenarios and assist their growth.
  • Intensity: The light intensity should be maintained at a relatively low level to avoid inducing stress. Some aquarium enthusiasts utilize a lower wattage bulb or drape a cloth over the aquarium to reduce the light.
  • Darkness: Ensure a duration of darkness for rest and to imitate their natural habitat. This period can last for about 12-14 hours each day.


For those of you who are in a rush, here is a quick roundup of what I discussed earlier:

  • Molly fish require properly managed light, mimicking their natural day-night cycle, to support their biological rhythms and overall health.
  • The right light conditions contribute to mimicking their natural habitat, promoting healthy activity, enhancing color vibrancy, supporting plant life, and aiding in temperature management.
  • Molly fish typically need around 8-12 hours of light per day, followed by a period of darkness for rest and recovery, to thrive.
  • LED lights are advantageous for molly fish due to energy conservation, minimal heat emission, and enhanced color display.
  • When selecting lighting, consider the type of light (such as LED lights), the color temperature (5000-7000K), and the intensity (moderate) to create a comfortable environment and replicate their natural habitat.