GloFish Denmark (Denmark Rerio) information and care sheet

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GloFish® Danios are not artificially colored or cruelly injected with paint. Instead, these fish are the result of genetic testing that led to their brightly fluorescent color range. If you are planning on getting one of these fish, knowing how to properly care for it is important, as their attractive colors have often resulted in many impulsive purchases.

Read on to find out everything you need to know about GloFish danios, why they fluoresce, and how to maintain a school of them in your own freshwater aquarium!

About GloFish Danios

You have likely seen these fish at your local pet store before as their mesmerizing fluorescent colors make them very difficult to miss. This fluorescence is the result of a temporary absorption of an electromagnetic wavelength, which is then released at a lower energy level, resulting in a different color.

Usually these fish are a common freshwater species like tetras, barb, or danios, unless they are a different color. These fish are part of the trademarked GloFish market.

How are GloFish Danios different from Zebra Danios?

GloFish offers a variety of freshwater fish species that have been genetically engineered to display fluorescent colors. Contrary to popular belief, these colors are not the result of dye injections and are passed down genetically.

In the scientific field, Danio rerio is considered one of the top model organisms for research. On the way, scientists injected a green fluorescent protein (GFP) into a zebra-danio embryo in the hope that the fluorescence would indicate toxins and pollutants in the immediate vicinity; This CFP was originally obtained from a jellyfish, mostly Aequorea victoria.

As genetically modified organisms became more closely studied and better understood, other genes were extracted and added to the Danio zebra, including those from a sea coral that resulted in red fluorescence and other orange and yellow variations of other jellyfish genes.

GloFish has taken these colors and developed Starfire Red®, Electric Green®, Sunburst Orange®, Cosmic Blue®, Galactic Purple® and Moonrise Pink® variations that are used in Danios, Tetras, Betta fish and more too are found. Unlike artificially colored fish, these fish are descendants of genetically modified adults, so the color is inherited and does not fade over time.

In the aquarium hobby, there is still some debate about whether or not to keep GloFish, but it is comforting to know that the fish have not been exposed to inhuman practices. If you are planning to fill an aquarium with these fish, knowing how to properly care for them is important.

GloFish Danio care

For the most part, each type of GloFish requires the same maintenance as its normally colored counterparts. The most important thing to keep in mind with a GloFish danio is that these fish come from cold water environments and require a lower temperature than most freshwater fish in the community.

Tank requirements

The zebra danio is a schooling fish that is very active in the aquarium. This means it’s best to keep them in as large a tank as possible, although a 37.9L aquarium will comfortably run a school of 10. A larger tank size will be required for any additional fish added beyond this.

Due to their high activity, these fish need a lot of open water in order to be able to swim and to show their natural school behavior. For the most part, these fish tend to cling to the top and middle of the water column. You will appreciate natural foliage in the form of live plants and a gravel or sand substrate; Most GloFish hobbyists like to keep their fish on a dark surface and under special LED lighting to bring out their fluorescence best.

Water parameters

The danio zebra is found in many countries in South Asia, including Pakistan, Nepal and Bhutan. They are particularly common in the catchment areas of the Ganges and the Brahmaputra. These regions are often cooler than tropical conditions, which makes both the Zebra Danio and GloFish Danio a cold water species.

In the aquarium, it is usually best to keep the water temperature between 20.0 and 22.2 ° C (68 to 72 ° F) with a relatively neutral pH between 6.5 and 8.0. However, due to the intensive breeding and adaptation by the hobby of the aquarium, these fish can usually withstand more tropical conditions. It is best to ask about the temperature of the tank in which they are kept to avoid bumps.

Otherwise, these fish will need stable water conditions with 0 ppm ammonia, 0 ppm nitrites, and maintained nitrate levels. A filter is needed, although heating may not be necessary given the climate of the place where they are stored. In general, even if you are holding a type of cold water, it is best to use an aquarium heater to keep the temperature stable, even if you are not using it to heat the water.

GloFish tank mates

As long as you have a decent number of danios, you can be sure to bring a good amount of cold water species with you. However, it is important to coordinate the active behavior of these fish with other fish to prevent the stress in the tank from increasing. For this reason, it is best to avoid slow moving and docile fish. There is also a chance that fish with longer fins will occasionally be pinched. Therefore, it is generally best to avoid these species as well.

As a cold water species, both zebra and GloFish danios are usually kept with other fish that also prefer less tropical tank conditions. The best GloFish danio tankmates make other danios (both zebra and GloFish colorations), corydoras, white cloud minnows and even some tetra species if the temperature requirements match.

GloFish Diet

GloFish Danios are not fussy eaters, although you want to make sure you are feeding a variety of foods that keep their red, orange, yellow, green, blue, and purple colors as light as possible. In the wild, these zebra danios are omnivorous, which means they eat both animal and plant-based foods.

In the aquarium, it is best to have a variety of live, frozen, and freeze-dried foods available to keep your fish interested and eat healthy. A high quality fish food such as flakes or pellets should be the main food. Other delicacies such as bloodworms, brine shrimp or mosquito larvae may be offered from time to time.

GloFish danio FAQ

Here are some questions to consider about these genetically modified fish before buying one for your own freshwater tank!

How big do GloFish Danios get?

GloFish Danios grow to be as big as normal Danio Rerio and reach an adult size of 5.1 to 7.6 cm. Although these are relatively small fish, it is important to consider that they will need to be kept in a larger school of at least six or more and a larger tank will still be needed.

How long do GloFish Danios live?

Unfortunately, GloFish Danios don’t live too long. On average, they live between 2-3 years, with 5 years being the extreme. However, genetic engineering is not believed to have affected the lifespan of these fish, as regular danio rerio only live a few years, even with perfect tank and water conditions.

How many GloFish Danios should be kept together?

Like Danio Rerio, GloFish Danios like to train together and become much more active in larger numbers. In general, it is best to keep at least six or more GloFish danios together to increase activity levels and prevent aggression.

Are GloFish Danios aggressive?

While both GloFish Danios and Zebra Danios are community fish, they tend to be more aggressive towards one another when kept in smaller numbers. This is most similar to a pecking order that leaves the weakest and smallest fish behind.

These fish can also be more aggressive if kept in a smaller tank that doesn’t have enough space for free schooling.

Can you breed GloFish?

No, you cannot intentionally or commercially breed GloFish. Since GloFish is a patented and trademarked trademark, breeding these fish is prohibited.

Otherwise, growing zerba danios is relatively easy and can even be done by yourself in your tank without intervention. You can find more information about breeding Zebra Danios in our complete Dani Rerio care sheet here.


GloFish danios, tetras, and barbs seem to be the by-product of something unnatural, but in fact, they’re not very different from their regular colored counterparts at all. However, some aquarium enthusiasts do not endorse the marketing of these fish.

In fact, these GloFish danios require the same diet, water parameters and tank maintenance as usual, although their cold water needs must be considered. It is also important to note that GloFish danios, tetras, barbs, and any other official GloFish species cannot be intentionally grown in the aquarium or sold.

If you have any questions about GloFish, Zebra Danios, or experience keeping other variations of these fish, don’t hesitate to leave a comment below!

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