Turtle lights should be on for about 12 hours a day and completely off at night. Most care guides land between 10 and 14 hours, depending on the species and the time of year, and that applies to both the UVB light and the basking (heat) lamp. The easiest way to get it right every day is to put both on a plug-in timer.
That’s the short answer. Below are the hours by species, what to do in winter, and what to do about warmth at night if you turn the heat lamp off.
Light hours at a glance
| Turtle or tortoise | Light hours per day | Lights at night |
|---|---|---|
| Red-eared sliders and other aquatic turtles | 11–13 hours, a little shorter in winter and longer in summer | Off |
| Box turtles (indoors) | 14 hours in summer, 10 hours in winter | Off |
| Russian tortoises | 14 hours in summer, 10 hours in winter | Off |
| Mediterranean tortoises (Hermann’s, spur-thighed, Horsfield’s) | About 12 hours, with the basking lamp on for at least 12 | Off |
The aquatic turtle hours come from ReptiFiles’ red-eared slider guide, the box turtle and Russian tortoise hours from ReptiFiles’ care sheets, and the Mediterranean tortoise hours from the Royal Veterinary College’s care sheet. If you’re not sure which group your turtle belongs to, a steady 12 hours on and 12 hours off falls within, or between the summer and winter figures of, every guide here.
How long should a turtle UV light be on?
Run the UVB light for the same hours as the rest of the daytime lighting: roughly 11–13 hours a day for an aquatic turtle like a red-eared slider, and about 12 for most indoor tortoises. UVB is part of the “daytime” your turtle gets, so it goes on in the morning and off at night along with everything else.
A few things decide whether those hours actually do anything:
- Nothing between the bulb and your turtle. UVB has to reach your turtle unfiltered. VCA’s vets point out that glass or plastic between the lamp and the animal blocks it, so a UVB bulb sitting on top of a glass lid isn’t helping much. A mesh screen matters too: ReptiFiles’ distance guidance assumes no mesh in the way, and a screen means adjusting the distance.
- The right distance. VCA suggests roughly 9 to 15 inches (23–38 cm) from the lamp to your turtle. ReptiFiles’ red-eared slider guide gives distances by bulb model and advises not mounting a UVB lamp closer than about 10 inches (25 cm) to the basking spot. Your bulb’s packaging is the final word.
- Over the basking spot. ReptiFiles recommends mounting the UVB lamp above the basking area, next to the heat lamp, so the UV is strongest where your turtle sits.
- A bulb that still works. UVB output drops as a bulb ages, and you can’t see it happening. VCA recommends replacing UVB bulbs every 9 to 12 months or as the manufacturer directs, and the Royal Veterinary College says to change them at least as often as the manufacturer recommends.
How long should a basking light be on?
The basking lamp follows the same schedule as the UVB light: on for the day, off at night. For aquatic turtles, ReptiFiles says heat lamps should be turned off at night. For Mediterranean tortoises, the Royal Veterinary College recommends a basking spot of about 95°F (35°C) kept on for at least 12 hours a day and switched off at night.
Your turtle uses the basking spot to warm up, then moves to cooler areas or back into the water. That only works when the warm spot is there during the day, so make sure it’s on before your turtle is usually up and about.
How long should a tortoise lamp be on?
Indoor tortoises need about 12 hours of light a day, and some keepers follow the seasons with longer summer days and shorter winter ones.
- Mediterranean tortoises: about 12 hours a day, with a high-output UVB lamp, according to the Royal Veterinary College.
- Russian tortoises: ReptiFiles recommends 14 hours a day in summer and 10 hours in winter.
Tortoises also benefit a lot from real sunshine. The Royal Veterinary College notes that safe, secure time outdoors in summer is valuable for their welfare. If you’re giving your tortoise regular outdoor time, keep the indoor schedule going on the days it’s inside. And while you’re building a routine, how often to soak a tortoise covers the other regular job tortoise keepers ask about most.
Can you leave a heat lamp on 24/7?
No. Turtles and tortoises need a proper night. ReptiFiles and the Royal Veterinary College both say to switch the lights off at night, and ReptiFiles warns against colored “night” bulbs too, even after dark. Red, blue and purple bulbs are still light, so they don’t give your turtle a real night.
Leaving the heat lamp on around the clock also takes away the nighttime temperature drop that turtles get in the wild. ReptiFiles’ box turtle guide recommends turning indoor heating off at night for exactly that reason, and its red-eared slider guide notes that water temperatures naturally fall overnight in the wild too.
What if my house gets cold at night?
If your room gets cold enough that the enclosure drops below a safe night temperature, add warmth that doesn’t give off light instead of leaving the basking lamp on. The Royal Veterinary College suggests options like room heating, a heat mat on the back wall, a tubular heater or a ceramic bulb, ideally on a thermostat.
How cold is too cold depends on the species, and the guides don’t all agree:
| Species | Night temperature guidance |
|---|---|
| Mediterranean tortoises | Not below about 64–68°F (18–20°C) (Royal Veterinary College) |
| Russian tortoises (indoors) | About 70–75°F (21–23°C) (ReptiFiles) |
| Box turtles | Tolerate nights as low as 50°F (10°C) (ReptiFiles) |
For aquatic turtles, ReptiFiles notes that hatchlings are very sensitive to cold water, so keep their water heater running overnight. A digital thermometer, or a min/max one that records the coldest point of the night, is the easiest way to know rather than guess.
Should light hours change with the seasons?
You can do either, and both are reasonable. VCA’s vets advise keeping lighting and temperatures consistent for indoor reptiles unless you’re breeding them. ReptiFiles prefers a seasonal rhythm: a shorter “day” in winter and a longer one in summer, such as 10 hours in winter and 14 in summer for box turtles and Russian tortoises.
If you’re new to this, a steady 12 hours all year is the simplest choice and fits every guide above. If you’d like to follow the seasons, change the timer a little at a time between summer and winter rather than jumping from 14 hours to 10 overnight.
Shorter winter days are not the same thing as hibernation (brumation). That’s a separate decision with its own preparation, and not something to start by changing the lights.
Set it and forget it: using a timer
A timer is the easiest way to keep the day the same length every day. ReptiFiles recommends a digital or smart plug timer for both the UVB lamp and the heat lamp, so the lights switch on and off on time even when you sleep in or travel.
A simple 12-hour schedule looks like this:
| Time | What happens |
|---|---|
| 7:00 a.m. | UVB light and basking lamp turn on |
| Daytime | Your turtle basks, eats and swims or roams |
| 7:00 p.m. | All lights turn off |
| Overnight | Dark. Lightless heat only if your room gets too cold |
Pick times that match your household, so the lights are on while you’re around to feed and check on your turtle. How often to feed a red-eared slider has the schedule for sliders, and how often to change turtle water covers the other half of a tank routine.
A quick lighting checklist
- Lights on about 12 hours a day (10–14 depending on species and season), on a timer.
- UVB and basking lamp over the same spot, on the same schedule.
- No glass or plastic between the UVB bulb and your turtle.
- UVB bulb replaced on schedule, even if it still lights up.
- Lights fully off at night, with no colored night bulbs.
- Lightless heat only if your room gets colder than your species needs.
The bulb replacement is the step people forget, because nothing looks wrong. If a sticky note on the tank isn’t your style, ShellPal can remind you when a UVB bulb is due.