Glofish Care Guide

Photo credit given to the Glofish Company.

If you live in the United States of America, chances are that you have walked into a local pet shop or supercenter store and found yourself staring at small fish magnificently decorated with neon colors of red, green, orange, pink, or purple. Personally, I fell in love with a pink Glofish just like the photo above, brought her home, and named her Bubbles. Glofish are beautiful and great pets, but If you thought such vivid colors on Glofish seemed unnatural, you would be correct. Changing the genes of animals is an ongoing scientific controversy that is popular with some biologists seeking gene research. In this article we will cover where Glofish come from, the controversy of Glofish selling, and lastly how to care for Glofish in your home aquarium.

Where Do Glofish Come From?

Ten years ago, scientist Dr. Zhiyuan Gong along with his team from the National University of Singapore sought a way to detect pollution in bodies of water. The team experimented by extracting a green fluorescent protein gene from a jellyfish, and integrating into the genome of a zebrafish embryo. The result was astounding in the field of science: the fish was born with fluorescent skin. The zebrafish would appear brighter(fluoresce) in contaminated water, and not fluoresce in safe water.

The appearance of neon fish excited consumers and businessmen alike. Alan Blake and Richard Crockett of Yorktown Technologies signed contracts and exchanged money with the scientists from the National University of Singapore to be able to market Glofish.

The Scientific Controversy of Glofish

In the early stages of trying to sell the Glofish, the businessmen ran into obstacles with the United States Food and Drug Administration and the Center for Food Safety for questioning morality. Joseph Mendelson of the Center for Food Safety stated:
It’s clear this sets a precedent for genetically engineered animals. It opens the dams to a whole host of nonfood genetically engineered organisms. That’s unacceptable to us and runs counter to things the National Academy of Sciences and other scientific review boards have said, particularly when it comes to mobile GM organisms like fish and insects.

This statement was disregarded. Eventually, the FDA in December of 2003 determined that:

Though the FDA allows Glofish distribution, the United States has less strict regulation than many other countries in the world. For instance, Canada and the European Union strictly ban genetically modified organisms because they do not know how GMOs will affect health in future years, and because they consider GMOs somewhat inhumane. This being said, Canada and the European Union ban the “GMO fish” from their country.

Glofish Rise to Popularity

Between 2012 and 2014, soon after gaining rights to distribute Glofish in the United States, Yorktown Technologies began selling new breeds and colors of Glofish: electric green black tetras, electric green tiger barbs, sunburst orange tetras, and moonrise pink tetras, starfire red tetras, and cosmic blue tetras. The colors are brilliant and interesting as they are genes extracted from sea corals and creatures such as sea pansy, mushroom corals, sea anemones, chalice coral, brain coral, and various jellyfish species.

As Glofish gained popularity, the Glofish Fluorescent Fish License was created, establishing that:


Some aquarium enthusiasts think Glofish may be sterilized to prevent distribution outside of the company. Though, this theory is less strong because there have been many cases where people find that their Glofish purchased from a pet store are, or become pregnant.

Benefits of Glofish Research

The invention and study of Glofish have led biologists to discover that there are in fact species of fish found in nature that share a fluorescent gene similar to that of Glofish, but less dominant. Studies have actually aided in understanding cellular disease, cancer, and gene therapy through observing fluorescent, easy to see cells. The American Museum of Natural History has discovered approximately 200 species of fish that are naturally fluorescent. The genes most obviously appear under blue lighting. This is because in the photic layer of ocean water, no other wavelengths of light besides blue can reach high depths. Fish absorb the high energy blue light, and re-emit a lower intensity energy that produces a different color reflection. Blue light shows fluorescence the best in fish, and that is why the Glofish company promotes blue lighting for their fish.

When establishing your Glofish’s environment it is important to think of the habitats of their ancestor species: zebrafish danios and longfin tetras. History can tell much about both behavior and preferences of the new fish species.

Zebrafish Danio Origin

Zebrafish danio, also known as “striped danio” have the scientific name danio rerio, and are indigenious to Asia in Pakistan, India, and Myanmar (Burma). These fish live in tropical rivers with fast moving water, which is why they prefer temperatures around 78 degrees as well as water movement in the aquarium. Rivers also provide abundant leafy plants as well as plants such as Water Wisteria, Hornwort, and the popular Java Moss.

Zebrafish danio are typically peaceful, but once in a while a fin nipper can be spotted of their kind. Compatible tank mates to zebrafish danio would be tetras and crydoras. Zebrafish danio are a lively breed of fish, so be careful of them jumping out of your tank. As a freshwater river fish, watch for freshwater fish disease if your fish seem to get sick.

Gender difference can be told because female zebrafish danios are larger and have a more pronounced stomach in which to carry eggs.

To mate zebrafish, keep a constant temperature of 78 degrees Fahrenheit in your aquarium, along with having a pair of zebrafish that seem friendly and of opposite sex. After the female lays eggs, quickly remove them and place them in an isolation tank because the adult zebrafish will feed on the fry. The eggs take 2 days to hatch.

Longfin Tetra Origin

Longfin tetras, scientific name ternetzi have developed into many different variations of tetras including skirt tetras, black widow tetras, and Glofish. Longfin tetras are found naturally in South America in the basins of Paraguay and Guapore. The fish live in slow moving streams near forests. Here, longfin tetras freely feed on worms, insects, and small crustaceans.

Longfin tetras grow to be 2.25 inches long, and live an average of 6.5 years. These fish are semi-aggressive, very hardy, and adapt well to most water conditions.

Since they originate in warm South America, longfin tetras prefer water between 70 and 80 degrees Fahrenheit. They prefer a lot of clumped vegetation, low to the ground and leaving plenty of swimming space.

Starfire Red Danios

Photo credit given to the Glofish Company.

Glofish Care
Glofish Care Do’sGlofish Care Don’ts
  • Give your Glofish plenty of space. The ideal aquarium size for glofish is 10 gallons or more
  • Keep your Glofish in a small tank. While Glofish can survive in very small tanks, they do not enjoy it as they love swimming space
  • Keep the temperature between 72-80F
  • Fluctuate the temperature
  • Keep the water too hot/cold
  • Use medium flow filters to create current and to keep your tank water clean
  • Provide no filtration for your water, or no current. Glofish love current as it is naturally occuring in their wild habitat
  • Keep Glofish in “schools” of 5 or more
  • Pair Glofish with aggressive fish
  • Feed your Glofish one flake per fish twice per day
  • Feed your Glofish until it no longer accepts food. This contaminates the water with ammonia which is poisonous to fish.
  • Give your Glofish plenty of leafy plants
  • Provide no plants. Glofish like peaceful hiding places to sleep

Glofish are available in six eye-popping colors:

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

Glofish can be found in most pet stores or super center grocers for around 8 dollars. They are schooling fish, and love to abide in groups of 5 or more per aquarium, though not mandatory. If purchasing Glofish, take note that electric green tiger barbs may become aggressive if not kept in groups 5 or more. Other Glofish breeds are usually peaceful in both small and large numbers. Glofish typically live 2-4 years, and grow up to 2 inches long. These fish are moderately hardy, and are easy to care for. They are also great pets to have as they are active swimmers; very entertaining to watch. To tell the difference between male and female, look for the larger, more pronounced stomach of the female Glofish.

When bringing home Glofish, be sure to float their bag in the aquarium for 30 minutes, and then add 1 cup of water every 10 minutes until the bag is full. This will ensure no quick temperature changes, and will keep your fish safe during its transfer to your aquarium.

Glofish specific care guidelines are as follows:

Aquarium Size: Ten gallons or more for a group of Glofish. This ensures they have space to swim and also ensures that your tank does not get an ammonium buildup and turn deadly to your fish. Make sure your tank is not located in direct sunlight or near a heating or cooling source as that may cause quick temperature swings that could prove fatal for your Glofish.

Temperature: Keep the aquarium their preferred temperature: a constant 72-80 degrees Fahrenheit.

Food: Provide tropical fish flakes (one flake per fish per day) and once in a while supplement brine shrimp for food. Glofish have big mouths, and will suck a whole flake in at the top of your tank seconds after you give them flakes. They seem like mini, colorful sharks when given food.

pH: Maintain a pH of 6.5 to 8: Glofish are pretty hardy, allowing them to handle a greater pH range than most fish.

Lighting: Keep aquarium light on for 10-14 hours per day. White LEDs look great with Glofish as well as Glofish blue LEDs for showing off their vibrant neon colors at night.

Water Changes: Change water 25 to 50 percent of the tank each month.

Water Hardness: Keep water hardness between 5 and 19 dH.

Plants: Keep leafy plants as these are found in their natural habitats in rivers. Good choices are the java fern, scarlet temple, and anubias.

2 thoughts on “Glofish Care Guide

  1. Rebecka

    I’m am watching 4 GloFish for a friend and I’ve noticed the blue and pink one are being mean toward a green and white one. They won’t allow them to the front of the tank (also where I have kept the food and feed them) I have understood that thy prefer to be in bigger groups. So that’s understandable behavior
    However, with the green one I’ve noticed a difference in behavior (before he would constantly fight with the blue one to be allowed up front, or try swimming in the corner of the back to get away) now he’s under a small castle we have in the tank and hardly came out this morning for feed. (The other fish won’t fight when being fed) I noticed this morning when he did come out that he was very low to the ground and that his eye seemed to be covered in this oval bubble. I wouldn’t even say it was cloudy, but covered in a bubble.
    I’m wondering if this might be trauma from the blue fish aggressively nipping at him, pushing him up against the wall? Or perhaps an infection from that or something else?
    I’m worried about him because I do care for the fish.

    Thank you !

    1. Joshua@themandaringarden Post author

      Sorry that I am so late to answer, as this would need to be addressed right away. If this aggression is causing the fish harm I would try adding more large decoration in the tank to help create zones for the fish. I have noticed that my largest pink tetra would harass the smaller green one a lot. Adding a tall java fern stopped the issue for me.


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