what lights do hermit crabs need?

Do You Need a Light for Hermit Crabs?

Last Updated on: 3rd September 2023, 02:48 pm

Hermit crabs aren’t accustomed to lamps and artificial light sources. Too much light can be stressful. Pet hermit crabs need the right balance between light and darkness.

Hermit crabs need a natural cycle of 12 hours of light and 12 hours of dark because these conditions replicate their living conditions in the wild.

Never leave a lamp on overnight in the enclosure. Instead, placing the tank in a room with a window enables hermit crabs to follow their natural circadian rhythms.

Do Hermit Crabs Prefer Light or Dark?

Hermit crabs are nocturnal creatures, emerging at dusk to scavenge for food. In the wild, land hermit crabs spend their days buried under the sand to avoid exposure to predators and the sun’s rays.

To say that hermit crabs prefer darkness is an oversimplification.

Like all animals, hermit crabs are governed by their body clock. So, they must be able to differentiate between dark and light to understand when they should sleep and become active.

If you keep captive hermit crabs, you’ll unlikely see much of them during daylight hours. Even by night, hermit crabs may not emerge in a brightly lit room.

Are Hermit Crabs Sensitive to Light?

The eyes of hermit crabs are light sensitive, so excessive illumination causes hermit crabs no end of distress. Hermit crabs are used to moving, eating, and interacting in darkness.

Hermit crabs dislike too much bright light. If you shine a light toward the eyes of a hermit crab, it’ll retreat into its shell. Force them to endure light permanently, and they’ll grow confused and disoriented.

Hermit crabs will grow reclusive, stressed, and unwilling to eat/drink. Eventually, they may take drastic action to escape light, including severing their eyestalks, which may not grow back during a molt.

do hermit crabs need a light at night?

Do My Hermit Crabs Need a Lamp in Their Aquarium?

Lamps and artificial light sources are optional but can harm hermit crabs if used incorrectly.

As discussed, hermit crabs grow stressed when exposed to excessive light, and this stress will be magnified if the light source is artificial. As per Behavioral Processes, hermit crabs often respond to illumination with fear-based hiding.

Hermit crabs have excellent night vision, so a lamp left on overnight won’t be a source of comfort. Hermit crabs prefer darkness to know when it’s time to awaken.

Placing a hermit crab enclosure in a room with a window will provide lots of light, which will help hermit crabs maintain their natural circadian rhythms.

Any artificial light is more likely to unbalance hermit crabs’ sleep-wake schedules.

Do Hermit Crabs Need Light All the Time?

A constant light source in an enclosure is detrimental to the health of hermit crabs. Hermit crabs’ needs will be met if you choose an aquarium and location with sufficient access to natural sunlight.

Artificial light sources don’t just originate from lamps you switch on and off. For example, streetlights outside a window can also cause distress to hermit crabs.

If you live in a part of the world with extended hours of sunlight, use blackout blinds or curtains to provide optimal amounts of light and dark.

Do Hermit Crabs Need a Light at Night?

You may notice that hermit crabs are clumsy, spilling food and water overnight. This isn’t because they can’t see, though.

Hermit crabs seemingly constantly bump into water bowls and each other at night.

Surprisingly, this is usually intentional. Hermit crabs play by testing strength, colliding into each other’s shells. They also deliberately spill water to add moisture to the substrate and increase humidity.

According to the Journal of Comparative Physiology, hermit crabs have refracting superposition eyes containing cylinders and corneas that reflect light. Also, these cylinders store dim lighting.

You’ll notice that hermit crabs have large, round eyes. This is by design, as it enables hermit crabs to absorb and reflect ambient light, which means that hermit crabs can see well with little light.

Hermit crabs don’t rely on vision to negotiate their surroundings. All hermit crabs have antennae, which are linked to touch and scent, and these senses are more important to hermit crabs than eyesight.

Light Options for Hermit Crabs

Hermit crabs don’t need artificial illumination, so the lighting in a hermit crabs tank must be done under advisement. If you add a lamp, ensure that you select the safest option.

Ultraviolet Lights

Of the artificial light sources available to hermit crabs, ultraviolet light is considered the safest. Wild hermit crabs will be exposed to UV light through the sun’s rays.

However, as per the Woods Hole Oceanographic Institution, UV light only penetrates the upper 200 meters of the ocean. Marine hermit crabs dwell on the seabed, far away from sun exposure.

There are three types of ultraviolet light:

UVA:This is the longest wavelength of the sun’s rays, causing wrinkles and premature aging in the skin.
UVB:This causes the skin to burn but provides the vitamin D3 needed for calcium absorption.
UVC:This rarely reaches the atmosphere, usually failing to penetrate the ozone layer.

High UVA output harms hermit crabs’ eyesight (ocular health).


There are more benefits to a UVB lamp than any other form of artificial light.

The sun’s rays are a source of vitamin D3, which is required for calcium absorption. Without vitamin D and calcium, the exoskeleton would be compromised.

Unfortunately, too much UVB light will dry out the skin and gills, leading to suffocation.

If using a UVB bulb, consider placing it outside a glass tank. According to Photodermatology, Photoimmunology, and Photomedicine, a glass aquarium offers a protective barrier from UV rays.

Halogen Lamps

If you have a lamp with a halogen lightbulb, you may consider adding it to a hermit crab enclosure, as this will provide light while the lampshade provides a hiding place.

Unfortunately, halogen lightbulbs are a safety risk because they run extremely hot. Also, halogen lightbulbs tend to be vulnerable to breakage.

The heat produced by a halogen lightbulb isn’t sufficient to warm a hermit crab enclosure, but it’s an additional heat source. This can tip the balance between being too hot or too cold.

Hermit crabs will likely prod and poke a halogen lightbulb. If they don’t burn themselves, they may shatter the bulb, which is an obvious safety hazard. 

do hermit crabs prefer light or dark?

LED Lights

Are LED lights safe for hermit crabs? LED lights are cooler to the touch and virtually shatterproof, so hermit crabs won’t be able to break the bulb and won’t be subject to excess heat.

Heat Lamps

Hermit crab enclosures must remain above 80 degrees Fahrenheit. Unfortunately, heat lamps aren’t the most effective way to give hermit crabs additional warmth.

Hermit crabs prefer a steady and consistent distribution of heat. Consequently, hermit crabs can experience drying out of the gills if continuously exposed to a direct heat source.

Choose the lowest wattage if you use heat lamps in a hermit crab enclosure. Never point the bulb directly onto the substrate, leading to burns.

Making Lights Safe for Hermit Crabs

Hermit crabs may not need artificial light if they have a light-dark cycle of 12 hours each. Lighting only becomes necessary if the tank has limited or restricted access to natural light.

To keep hermit crabs safe, follow these guidelines:

  • Avoid trailing cables with live electrical cables.
  • Don’t allow hermit crabs to access light bulbs directly.
  • Avoid brightly colored bulbs as they may provoke a startled response.
  • Keep light wattage low.
  • Never expose hermit crabs to 24-hour illumination.
  • Avoid shining high-powered heat lamps onto the tank.
  • UVB light is beneficial as it provides vitamin D3.

Hermit crabs have a complex relationship with light. The simplest way to judge the illumination needs of hermit crabs is to imagine they’re still living in the wild.

In their natural habitat, hermit crabs rely on natural light patterns. So, replicate them to keep captive hermit crabs happy, strong, and healthy.