Freshwater Fish

How To Breed GloFish Species: What You Need To Know


GloFish are unique fish that don’t exist in nature because they were created by genetic manipulation. GloFish is a term used to describe more than one species of fish that has been genetically modified so as to express a fluorescent color. They are fluorescent fish that all live in freshwater and are found in the aquarium industry.

You probably are curious then as to how you would go about breeding GloFish considering they are not your typical fish species.

In this article, we will describe how to breed GloFish with details and tips on each species in terms of what is needed in each case in terms of water temperature and for egg-laying.

Breeding GloFish

The method for breeding GloFish depends entirely on what species of fish it is. This means that breeding a GloFish Danio will vary somewhat from breeding a GloFish Betta.

You do need to realize that the fluorescence gene giving the fish a glow may not be passed to all of the fish’s offspring. To ensure the gene is 100% passed on to the offspring would require a knowledge of exactly how the gene is inherited in each case.

The precise way in which each species of fish used as GloFish is bred varies because they have different requirements and aspects of their reproduction. GloFish breeding behavior and needs will be discussed below.

General Tips For Breeding GloFish

For most of these GloFish, changing the water in the tank and feeding the fish lots of protein-rich food like bloodworms, tubifex worms, Daphnia, or mosquito larvae, can help to encourage reproduction.  

GloFish also produces pheromones when ready to reproduce which acts to stimulate the production of the eggs by the female, and the later fertilization of eggs by the male.

One thing all GloFish have in common is that they do all lay eggs, which can be a problem

because the adults may end up actually eating their own eggs.

Filtration systems should include using a sponge so that if any eggs or fish fry are produced, they don’t get sucked into the filter system.

Read further to learn about each of the five GloFish species and what conditions they would most likely reproduce in.

Breeding GloFish Danios

Danio rerio, the zebra danio, is the species that is used to produce GloFish danios. Danios require a tank that is a minimum of 10 gallons in size if you have any hope of them trying to breed.

The GloFish zebra danios are peaceful non-aggressive fish that like to school. You can keep them in a tank with other fish that are of similar size but that won’t attack or feed on them.

Of course, for breeding purposes, you will not want other fish to be present and should follow the suggestions we have given for breeding this species.

Danios do better in water that is slightly soft and also a bit on the alkaline side, so a pH of 7.0 to 7.8 will suit them better. The temperature of the water should be no higher than 78o F and no lower than 70o F.


A female danio will produce and hold the eggs in her body anywhere from 7 to 14 days. She can lay up to 400 eggs, but these are not put in one place. Instead, the female danio is known as an egg-scatterer, as in she releases and scatters her eggs throughout the tank.

A useful substrate is one made of marbles so that any eggs that are released can sink between these and will not be easily eaten by the adult fish.

Plants can also be added to the tank. These can help provide some hiding spaces for the fish fry.  

It is advisable to remove the parents from the tank once the eggs have been released. Egg hatching takes place anywhere from 36 hours to 48 hours afterward.

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how to breed glofish

Breeding GloFish Tetras

Gymnocorymbus ternetzi, also known as the black skirt tetra or petticoat tetra, is another species that was modified to produce a GloFish. This species, similar to the GloFish danio can breed in a 10-gallon or a 15-gallon tank.

They are small fish, getting no larger than about 2 to 2.5 inches. They do best in soft water that is kept at a water temperature of between 70 oF to 75oF.

Artificial grass or spawning mats can be placed in the tank along with marbles to prevent the parent fish from finding and consuming any eggs.

The marbles provide a good barrier because the eggs often fall behind these or below them making it harder for the fish to find them and eat them.


Male tetras have slimmer bodies than the females and when the females are gravid (carrying eggs), the body becomes rounder and larger. Tetra males also have a more pointed appearance to the anal and dorsal fin.

Females lay eggs on spawning mats or on the substrate. The male then fertilizes them when he swims over the eggs.

Since the tetras are likely to eat their own eggs or fry, it is best to quickly remove the parent fishes and transfer them into another tank.

Breeding GloFish Bettas

Bettas (genus Betta) can be kept and reared in a similar size aquarium to danios and tetras. One consideration with bettas is that a male and a female can become aggressive when they are first placed together in a tank, which means you need to keep a close watch on the fish.

In fact, bettas are also called fighting fish by some people due to their territoriality and aggressive tendencies. Males are particularly territorial so you can not keep two males together at any stage.

It is important to note that bettas often prefer slightly warmer water to tetras and danios, with temperatures preferred at or between 77oF and 80oF.

Courtship And Egg-laying

Bettas have interesting reproductive behavior. The male bettas have more elaborate fins than females, which he uses in courtship behavior. The male betta also courts the female by producing what is called a bubble nest. He makes this by creating a structure from bubbles.

This is supposed to impress the female enough that she will lay eggs. The male will court the female and then at some point wrap his body around hers. The female then will release the eggs that the male collects.

He uses his mouth to collect the eggs which are then placed in the bubble nest. Bettas can release eggs every 2 or 3 days when they are breeding.

The female needs to be removed after laying eggs but the male should remain so that he can care for the eggs. Once the eggs have hatched the male can then be removed from the breeding tank.

Breeding GloFish Barbs

The GloFish barb was created using the tiger barb fish, Puntigrus tetrazona. Different color GloFish barbs have been created including a green, sunburst orange, and red fish.

These are quite adaptable fish that can tolerate a greater range of water hardness than the other species of GloFish that are sold. They do survive best in water that is kept between 72 oF and 82oF,

There are similarities when breeding this GloFish compared to the other species that can be reared. For example, a similar-sized tank of about 10 gallons will do.


Some of the same challenges exist when it comes to the parent fish wanting to cannibalize on their eggs.

Eggs of the barb are also scattered around during egg-laying. Fish need to be taken out once eggs are laid to again avoid the issue of parent fish eating their own eggs or fry.

Breeding GloFish Sharks

The likelihood of being able to successfully breed GloFish sharks in captivity is actually very low because, to begin with, you need a lot of space and they are not easy fish to deal with.

These are not actual sharks but rather in the family Cyprinidae. The GloFish shark is a modified rainbow shark, Epalzeorhynchos frenatum.

The tank needs to be big since they grow up to 6 inches. It is recommended that an aquarium be at least 75 gallons in capacity. The temperature of the water should be between 71oF and 85oF.

Hormones And Egg-laying

These sharks need to be treated with hormones to stimulate reproduction. This requires special knowledge and experience to achieve the desired result.

Unlike other GloFish, the GloFish sharks are very unlikely to produce eggs on their own without careful human intervention.

Sharks can also quickly turn aggressive towards each other making mating tricky. If a pair of GloFish sharks do bond then the female will carry eggs for about 2 weeks before laying. The eggs are then fertilized right away by the male shark who swims over them.

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Sharks, like all the other GloFish species we have mentioned like to feast on their own eggs, so you definitely cannot leave the adults and eggs in the same tank. The eggs should be removed and put in a smaller 10-gallon tank.

glofish breeding behavior

A Guide To Caring For And Setting Up GloFish For Breeding

Regardless of whether your fish breed or not, you will need to know how best to care for them. Below we discuss what you need to consider once you know how to breed the GloFish species you have.


GloFish can be housed in tanks that are at least 10 gallons except for the sharks, which require more space. In general, a bigger tank, of at least 20 gallons is probably a better option when keeping fish, but this also depends on how many fish you plan to keep.  

When it comes to tank shape avoid odd shapes like the hexagonal tanks. These may make good conversation pieces but there are some notable drawbacks.

These tanks have less space and there is also the difficulty of cleaning them. Rectangular tanks are easier to clean and provide more of the length needed by actively swimming fish.


The substrate choice can be either sand or gravel but sand can be messy. However, it may be easier to clean the sand because dirt accumulates on top and does not penetrate through in the way that it does with gravel.

Sand substrates tend to look less attractive and become dirty-looking faster than gravel. Marbles can also be added to the top of the gravel which can make the tank look more attractive and helps if fish do lay eggs.


Decorating your GloFish tank comes down to personal choice. There are a number of backgrounds you can use and stick behind the aquarium. Any background with black and blue colors can help accentuate the glowing of the fish, but it is up to you.

Decorations inside the tank are also a personal choice and can include anything you want. Do keep in mind that décor will need to be cleaned regularly so the more you have and the more complicated, the more time will be required to keep everything clean.


You need to choose between artificial plastic or live plants. Live plants will make the aquarium more natural for the fish but artificial plants may be easier to control since they do not grow or die.  

Artificial plants also will not be fussy about water conditions or lighting while live plants have their own requirements needed to survive and grow.

Be careful not to put so many plants or other décor in the tank that the fish have little space left to swim.


You can use normal aquarium lighting or blue light. The blue LED lighting tends to highlight the fluorescence of the fish and if you really want the colors to glow you should use a black light.

Some aquarium enthusiasts like to use a mixture of blue and white LED lighting systems to highlight their fishes’ fluorescence.

Filtration System

You will need some type of water filtration system to remove pollutants and chemicals that build up, like ammonia and nitrites.

A sponge filtration system is recommended, particularly if you think your fish may breed. Other larger filtration systems may be needed for bigger tanks and an over-the-tank type filter system will also work well.

Heating System

We have given the optimal temperatures for the different species of GloFish and, in general, a heater is advisable to ensure that water is kept within the range that is best for the specific species of GloFish that you have.

  • The recommendation is to use a 100-watt heater in 20-gallon aquaria where the species is a tetra.
  • Danio GloFish can cope with a cooler temperature so a 50-watt heater will work.
  • For barbs and sharks, the recommendation is a 150-watt heater for fish kept in a 30- gallon tank.
  • For sharks, a 250-watt heater is suggested for a 50-gallon aquarium.

Tank Cycling And Fish Introduction

Before adding GloFish, the tank has to be cycled. This means that the water in the tank needs to be treated appropriately and then it needs to sit for as long as needed until the chemical parameters such as the water hardness, nitrate, ammonia, nitrite, and pH are at the correct levels.

Fish then need to be acclimated before being added to the water by floating them in the bag on the surface of the water for at least 15 minutes and slowly adding tank water to the water in the bag. Do this a few times and then after about another 15 minutes fish can be released into the tank.

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Cleaning your GloFish tank regularly is important if you hope to keep your fish healthy. This should be done on a regular basis, and at least every second week.

Avoid using any type of soap when cleaning the tank or décor because this will be toxic to

glofish tetra male or female

How GloFish Came About

Scientists at a university in Singapore were the first to learn how to genetically modify and create GloFish. The very first species of GloFish to be sold to the general public was the zebra danio, D. rerio.

The fish can glow because a fluorescence gene was inserted into the genome while the fish was an embryo. This gene is then inherited and passed on to future generations of fish during reproduction.

The original intent behind developing fluorescent fish was to use these animals as indicators of pollution with the idea that the fish would produce light and fluoresce when toxins were present in the water.

The scientists first used a green fluorescent protein extracted from a jellyfish and then later used a red fluorescent protein found in corals. Today, at least five species of fish have been modified to produce the GloFish species.

Fluorescent Genes

Research using fluorescence had been ongoing for many years before the development of GloFish. In fact, fluorescent genes are often used in studies of development.

The green fluorescent protein is used by scientists to study aspects of embryonic development. However, creating GloFish was a different idea and an extension of science.

GloFish has become a designer fish that people like to keep. They are attractive and beautiful little fish that can be easily kept provided it is legal to do so where you live.

Concerns About GloFish

GloFish are genetically modified organisms, which does pose ethical problems for some people.

However, scientists do not believe that Glofish poses any threat to wild populations of fish because experiments indicate that they do not proliferate when kept with the original wild-type fish species.

GloFish, like all aquarium fish, is not meant to be released into the wild, and this is a practice that should not be encouraged because in the future this could prove disruptive to natural populations despite what past experiments may indicate.


GloFish are fish genetically modified to express a fluorescence gene, with the original idea being to use glowing fish to indicate toxins in the water.

The fish species used today as GloFish in the aquarium trade include common freshwater fish, namely danios, tetras, barbs, bettas, and sharks.

Knowing how to breed GloFish is useful but it is difficult to do because the species tend to eat their own eggs, which means that adults need to be removed quickly from the breeding tank.

Frequently Asked Questions

How Do GloFish Get Pregnant?

GloFish are not live-bearing fish. In other words, the female of the species cannot carry and give birth to live fry. GloFish species are all egg layers, which is important to note when learning how to breed Glofish.

How Can You Tell If GloFish Are Male Or Female?

Differentiating male from female GloFish depends on what species of fish you are dealing with.

Male GloFish in the case of the tetra are smaller than females and have different stripes. In general, comparing the size and markings on fish can help you distinguish males from females.

Is It Illegal To Breed GloFish?

Even though you may know how to breed GloFish you should note that it is illegal to breed GloFish to sell or trade. People who own GloFish may find that their fish do try to breed if they have a male and female present and the conditions are right.

The company that owns the GloFish license states that it is not legal to purposively breed GloFish, and they also should not be bred for sale. The legality of even owning GloFish varies.

Many countries do not allow the keeping of GloFish. There are certain states in the United States that prohibited GloFish until quite recently.

Do GloFish Need To Be In The Dark?

GloFish do not need to be kept in the dark. They should be kept in 12 hours of light and 12 hours of dark since the species concerned are not fish that live entirely in the dark in nature.

Are GloFish Injected With Dye?

GloFish are not fish that have been injected or infused with dye or any artificial coloring. The fluorescence is from gene manipulation that was done to the embryo, and as previously mentioned, the genes involved are found in nature.


Passionate fishkeeper. Nature lover. Creative thinker. Music junkie. Adventurer.

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