Are Red Lights Bad for Leopard Geckos?

Red night lights were standard advice in leopard gecko keeping for a long time. The idea was that geckos could not see red light, so you could use a red bulb for overnight heating without disturbing them. I used to follow this myself before the research became clearer. It turns out the premise is wrong, and the advice has not aged well.

The short answer: yes, red lights are bad for leopard geckos. They can see red light, it disrupts their sleep cycle, and there are better heating options that produce no light at all. This article covers why, and what to use instead.

Can Leopard Geckos See Red Light?

Yes. This is the core misunderstanding behind the red light recommendation. Leopard geckos are crepuscular animals, most active at dusk and dawn, and their eyes are highly sensitive across a range that includes red wavelengths. Their colour vision is weighted toward the blue-green spectrum and their sensitivity to red is lower than to other colours, but lower sensitivity is not the same as no sensitivity. They can detect red light, particularly at close range or higher wattages.

The idea that reptiles are blind to red light originated from older research on snakes and was incorrectly applied to geckos. Studies on gecko vision, including research published in the Journal of Vision, have since confirmed that geckos have functional photoreceptors sensitive to a range of wavelengths including red. A red bulb at close range in an enclosed terrarium is not invisible to a leopard gecko.

Why Red Lights Cause Problems

Sleep Disruption

Leopard geckos are crepuscular, not strictly nocturnal, but they still depend on a clear day and night cycle to regulate their circadian rhythm. Light exposure at night, even dim red light, signals daytime to the gecko’s brain and suppresses melatonin production. Melatonin is the hormone that drives rest and sleep. Suppress it consistently and you get a gecko that is chronically sleep-deprived and stressed, even if it does not look obviously unwell.

The effects build gradually. A gecko under constant red night lighting may start refusing food, become more reclusive, or show increased skittishness during handling. These are stress signals, and sleep disruption is one of the most common but least obvious causes.

Heat Without Light Is What They Actually Need

The main reason keepers used red bulbs was overnight heating. That is a genuine requirement. Leopard geckos need a warm side maintained at around 75 to 80°F overnight, with the cool side allowed to drop to the low 70s. The ideal night temperature for leopard geckos is well documented and a red bulb can technically hit those numbers. The problem is it produces light as a byproduct, and that light is the issue. The solution is not to find a light that geckos cannot see. It is to use a heat source that produces no light at all.

Fire and Burn Risk

Incandescent red bulbs run hot and create an intense localised heat zone directly beneath them. A gecko resting or sleeping under a red bulb pressed against the glass can sustain thermal burns, particularly on the underside and facial tissue. This risk exists with any overhead incandescent bulb but is worth naming specifically since red bulbs are often left on at night unsupervised and without a thermostat.

What to Use Instead

Ceramic Heat Emitter

This is the standard recommendation and the one I use. A ceramic heat emitter (CHE) screws into a standard dome lamp fitting, produces consistent heat, and emits zero visible light. It is the most direct replacement for a red bulb and does the same job of maintaining overnight enclosure temperature without any of the drawbacks.

Always run a CHE through a thermostat rather than plugging it directly into the wall. Without a thermostat it will run at full output constantly, which can overheat the enclosure on warmer nights. A simple on/off thermostat set to your target overnight temperature is all you need. The heat lamp guide covers CHE setup in more detail.

Under-Tank Heating Mat

A heating mat placed under one side of the tank provides belly heat, which is how leopard geckos warm themselves in the wild, from the substrate above sun-warmed rock and sand rather than from overhead radiant heat. Mats produce no light and run quietly overnight. Like CHEs, they should be used with a thermostat to prevent overheating.

Some keepers use both: a mat for belly heat on the warm side and a CHE to maintain ambient air temperature. That combination covers the full temperature gradient a leopard gecko needs without any light source after dark.

What About Deep Heat Projectors?

Deep heat projectors (DHPs) emit infrared-A and infrared-B radiation, which penetrates tissue more deeply than standard ceramic emitters. They produce no visible light and are increasingly used as an alternative to CHEs, particularly in enclosures where penetrating heat is a priority. They are more expensive than CHEs but are a valid option if you want to upgrade your heating setup.

What About Other Coloured Night Lights?

Blue and white night lights cause the same problems as red, and in the case of blue light potentially worse ones. Blue wavelengths are much more disruptive to melatonin suppression than red, which is why the same blue light at night that affects human sleep will affect a gecko far more significantly.

The answer to night observation is not to find a light that geckos tolerate better. It is to use an infrared viewer or simply adjust to observing them in natural room light during the crepuscular window at dusk when they are active. Leopard geckos are rewarding to watch at this time and do not need a spotlight to be visible. I find the early evening, with the enclosure light off and a dim room, is when they are most active and most interesting to observe anyway.

For a deeper look at how leopard gecko vision works and why their colour sensitivity matters for lighting decisions, see our article on whether leopard geckos are nocturnal and the UVB guide for the full daytime lighting picture.