Do Glofish Need Light at Night? {How Do GloFish Glow?}

Are you trying to decide if keeping fluorescent lights on through the night for your GloFish is actually good for them? Will turning off the lights affect their famous and desirable glow?

In this article, we’ll explore the topic of GloFish lighting and specifically if they need light at night.

Do Glofish Need Light at Night? No. GloFish, much like other diurnal fish, do not need lights on at night. They require 12 hours of rest at night without lights and 12 hours of lighting during the day.

How Do GloFish Receive Their Glow?

GloFish are actually trademarked by Yorktown Technologies L.P. They are genetically engineered through a process called “transgenic insertion”.

It all started at the University of Singapore where they injected a fluorescent protein gene from a jellyfish into Zebra Danio embryos.

At first, it was only a Zebra Danios that could be genetically engineered into a GloFish, but now several species including the following are now available as this trademarked fluorescent fish:

  • Tetras
  • Barbs
  • Bettas
  • Rainbow sharks

You can now purchase GloFish in six vibrant colors:

  • Starfire Red®
  • Electric Green®
  • Sunburst Orange®
  • Cosmic Blue®
  • Galactic Purple®
  • Moonrise Pink®

How Much Lighting Do GloFish Need?

The diurnal cycle of a glofish requires them to sleep or rest for 12 hours at night without any lights on. The remaining 12 hours represent daytime where low-lit LED aquarium lights should help bring out the vibrant colors of these GloFish.

Without adequate lighting, your GloFish may end with a lack of appetite or display lethargy. If you want your GloFish to thrive during their lifespan which is usually around 3 years, please keep adequate lighting in mind.

Why Do GloFish Need Lights?

Beginner aquarists are usually enchanted by the gorgeous colors that GloFish exuberate. They have taken over the fish keeping hobby for many younger enthusiasts.

It’s important that anyone interested in keeping GloFish understands the need for aquarium lights to help regulate their eating and sleeping patterns.

YouTube video

What Are the Best Lights for Glofish?

The most popular choice of lighting is a fluorescent blue LED light. It’s best to keep the rest of the room dim or dark to show off the bright neon colors of your GloFish.

It’s tempting to leave the LED lights on all night to show off their colors in dark rooms during the early morning hours, but this stresses out your GloFish just like many other aquatic life.

No matter which lighting you choose, it’s best to turn them off every night for up to 12 hours.

You can do so with an aquarium timer in case you are not available or you forget. It happens to the best of us.

What Happens If I Leave the Lights On All Night For My Glofish?

Undesired effects occur if you leave lights on in your aquarium throughout the entire night.

You are disturbing the sleep cycle of diurnal creatures including much of your aquatic life. Your GloFish may experience the following effects:

  • Lethargy
  • Shortened lifespan
  • Lack of appetite
  • Weakened immune system
  • Excessive hiding
  • Erratic swimming patterns
  • Loss of color
  • Cloudy eyes

Accidents occurring from time to time. You may forget to turn off aquarium lights. It’s best to get an the aquarium timer to prevent future mishaps. Your vibrant GloFish will thank you for it.

Why Are My GloFish Not Glowing?

A popular misconception is that GloFish actually glow. This is not the case and it’s a simple misunderstanding.

The fact remains that GloFish are fluorescent, meaning they can fluoresce and absorb light that we shine on them.

The lighting should be low in wattage like a blue or black LED light that it can emit back. This is what we commonly perceive as a glowing effect.

Another issue with GloFish who lose their fluorescence results from the following situations:

  • poor diet
  • stress
  • poor water parameters
  • fluctuating temperatures
  • overcrowding
  • lack of companionship
  • bullying
  • too much lighting

Remember to turn the lights off for 12 hours a night and always test the water chemistry to maintain optimal levels for happy GloFish to emit their fluorescent shine back at you.

Do GloFish Like Light?

We cannot ask a GloFish how much light they prefer or the exact wattage they would like, but we can judge the vibrancy of their fluorescent colors based on the type of lights we provide.

Through trial and error and lots of experience, hobbyists and the trademark owners at Yorktown Technologies L.P. recommend that we keep a low-light setting.

This way your GloFish can absorb and emit it back to us better than using brighter tank lights. Opt for LED lights that are blue or black to help your GloFish fluoresce with optimal shine or glow.

Will Blue LED Light Calm Glofish?

Too much lighting will not calm any fish. It may cause erratic swimming and stress.

Large amounts of blue lighting is proposed without enough evidence to suggest that it may affect their retinas.Simply turning off aquarium lights at night for 12 hours would mitigate this concern.

Blue lighting is calming and soothes the transition from daylight to nighttime. It’s an astringent effect that mimics a moonlight over the ocean.

Blue LED lights are the top choice of lighting for your Glofish.


As it stands, your GloFish are going to benefit from the same type of sleep pattern that the rest of your aquatic life are used to in a community tank.

Even if you are keeping only GloFish in your aquarium, make sure to follow the same type of 12 hours on and 12 hours off light cycle. Use an aquarium timer to help your GloFish remain healthy, hardy and vibrant.


Thanks for visiting for another article dedicated to GloFish that we research and keep. Our kids love them as well. See you soon for another article anytime you feel curious for more information. Bye for now!

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.

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