How many hours of light do goldfish need?
Mia Lopez
Updated on March 20, 2026
Use an automatic mains timer to give your tank between 12 and 16 hours of light each day, and 8 to 12 hours of darkness. Change your bulbs BEFORE they stop emitting light. This will keep your fish on schedule and keep the spectrum of your bulbs from changing too much as the bulb ages.
How long should I leave my goldfish light on?
In the wild, goldfish live in cool rivers, lakes and streams where they have regular access to relatively bright light. In captivity, their light cycle should mimic the lighting of their natural environment. Give your goldfish 12 to 13 hours of moderately bright -- but not hot -- light daily.Should I turn off the light in my goldfish tank at night?
Aquarium fish do not need light and it is best that you turn it off during the night. Leaving the light on can cause stress to fish as they need a period of darkness to sleep. Too much light will cause algae to rapidly grow and make your tank look dirty. So the short answer is no, do not leave your lights on.Do goldfish like the light on or off?
If your tank is in a poorly lit area – or if you want to grow live plants, such as hornwort – then it would be a good idea to include a light in your aquarium. Remember to switch off your aquarium light at night, as this will replicate natural day/night cycles. Like humans, goldfish prefer to sleep in the dark.How many hours of darkness do goldfish need?
Day and Night CycleFish do not have eyelids and rely on total darkness to rest. Without at least 8 hours of darkness, your goldfish can become sleep-deprived. This means you should turn off all lights before you go to bed to ensure your goldfish can rest peacefully.
Goldfish care - Do goldfish need light? - How much light is too much for your goldfish?
Do fish prefer light or dark?
Fish don't like the dark because when there is no light to see, they dart around the tank, colliding with the walls, ornaments and can even become tangled in the plants. Fish need light to determine whether it is night or day, and they're scared of the sudden switch from darkness to light.How do you know if goldfish is happy?
Your fish are happy and healthy when they:
- Swim actively throughout the entire tank, not just hanging out or laying at the bottom, floating near the top or hiding behind plants and ornaments.
- Eat regularly and swim to the surface quickly at feeding time.