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Why Did My Glofish Die? One Too Many Mistakes!

Why Did My Glofish Die? One Too Many Mistakes!

Credit: CBSC (CC License)

It’s really unfortunate that your glofish died an untimely death. But, even worse is the fact that one doesn’t get the proper closure they deserve when a pet fish dies. So, why did my glofish die? 

I wish I could pinpoint one reason and tell you right away why your glofish died. But frankly, there are often one too many reasons behind a fish’s premature death. 

Sometimes, it’s on you – other times, it’s just sheer bad luck. 

In this article, I’ll list down all the possible reasons behind your glofish’s death. 

You can then evaluate the reasons one by one and maybe be able to put your finger on them. 

So, let’s begin!

Why Did My Glofish Die?

The possible reasons behind glofish’s untimely death are:

  • Your fish was stressed
  • You didn’t cycle the tank 
  • Your tank is too small
  • You chose the wrong tankmates
  • Your feeding style is wrong
  • Your tank’s water is dirty
  • Water parameters changed too quickly
  • Your glofish made a long journey 
  • Your fish was diseased 
  • Your fish was old

Your Fish Was Stressed 

Stress is the numero uno factor behind a glofish or any other fish’s untimely death. While researching for this blog, I came across so many queries asking why my fish died a day after or a few hours after I brought him home.

And 9 out of 10 times, the answer is stress. 

We often underestimate a fish’s capacity to feel and perceive things, but in reality, they’re pretty intelligent beings. 

Therefore, just like us, they’re prone to stress as well. 

Sometimes, stress is an instant killer. Other times, it’s like a ticking time bomb. 

The reasons behind stress are as vague as they can get. It can be a lack of proper adaptation to a new environment, lack of enough space, aggression, poor water parameters, loneliness, and so on. 

And since fish aren’t as articulate with their expression as we’d prefer them to be, a newbie fishkeeper wouldn’t even know the fish is stressed until death is knocking on its door. 

Let’s have a look at the typical signs of stress in glofish:

Lack of appetite

Like all fish, glofish are opportunistic feeders. However, if they’re stressed, they may lose their appetite. They won’t show any interest even when you offer their favorite snack. 

And consequently, they will also lose some weight. I know you can’t really physically weigh the fish, but you can tell if they’ve shed some weight by just observing them. 

Glass Surfing 

The glass surfing behavior is characterized by the fish erratically swimming up and down the sides of the tank. 

Excessive Hiding 

Naturally, your glofish will resort to hiding when it’s feeling scared or uncomfortable. So retreating into one of the caves or behind the rocks once in a while is expected behavior. 

However, if you find your glofish constantly hiding most of the time, it’s a red flag.


In fish, stress and illness are like two sides of a coin. One cannot exist without the other. When your fish is stressed, the production of white blood cells in its system is inhibited. 

As a result, the fish’s immunity is compromised – making it susceptible to a plethora of pathogens waiting for the right moment to strike. 

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You Didn’t Cycle The Tank 

Not cycling the tank is the most common mistake new hobbyists make. But, frankly, setting up an aquarium the right way is not a walk in the park. 

You can just go ahead, fetch a glass tank, fill it with some tap water, add dechlorinator, and get done. 

Successfully cycling a tank takes several weeks – yes, you read that tight. 

In an uncycled or a wrongly cycled tank, death can happen overnight. Or, even worse, it will happen painstakingly slowly. 

It’s important to know that your glofish aren’t the only organisms that will be resigning in the tank. A healthy, fully cycled tank will also have a thriving good bacteria colony. 

These bacteria are present all over the tank but are primarily concentrated in the filter and the gravel. 

And their main duty is to break down the waste (leftover food and poop) to maintain the water quality. 

You see, glofish and good bacteria have a symbiotic relationship. 

The bacterial colony cannot survive without the waste fish produce. And without the bacteria, the water will quickly become inhospitable for the glofish. 

The hiccup here is that a newly set up tank doesn’t have a good bacterial colony yet. Therefore, you have to ‘cycle’ the tank to create it. 

And this process will take several weeks. So you really need to channel some patience here. 

I won’t go into the nitty-gritty of cycling a tank here. 

But I strongly suggest that you read up on the ‘nitrogen cycle’ before adding any more glofish into the tank. 

Your Tank Is Too Small

small glofish tank
Credit: Matt (CC License)

The minimum recommended tank size for a glofish shark is 50 gallons. For a single glofish betta, 5 gallons is recommended. 

As for the rest of the glofish species – danios, barbs, and tetras – you’d want to provide at least 20 to 30 gallons as these are schooling fish that need to be kept in a minimum group of 6. 

The ‘one inch per gallon’ rule is reportedly acceptable for fish under 3 inches. So, you can apply this rule to glofish barbs, tetras, and danios. 

However, would you put a 6-inch-long glofish shark in a 6-gallon tank? Or a glofish shark and 2 glofish tetras in a 10-gallon tank?

It might sound exaggerated, but an overcrowded tank is essentially a death sentence for your glofish. 

Beginner fish keepers often make the mistake of getting a tank first and then stocking it with inappropriate fish without researching their temperament and needs. 

In an overcrowded tank, glofish betta and shark’s aggression can get so high that it will often end with a bloodbath and the death of certain fish. 

And stress and aggression aren’t the only drawbacks of a small tank. 

Small tanks mean small colonies of good bacteria. And naturally, your fish will poop at a faster rate than good bacteria can break it down. 

And what happens next? The water will become so toxic that it will kill your glofish. No points for guessing.

I can go on and on about how small tanks can cut your glofish’s lives short – directly and indirectly. 

It will cause stunted growth, unsolicited aggression, stress, duels and injuries, and high levels of pollution – all collectively leading to your glofish’s untimely death.

You Chose The Wrong Tankmates 

Glofish sharks and glofish bettas are solitary beings. They don’t like to share their space with anyone. So, you don’t really have to worry about them getting lonely or bored. 

Instead, they’d be grateful to be left alone. 

On the other hand, glofish barbs, danios, and tetras are schooling/shoaling fish that should ideally be kept with their own kind. 

That being said, there are certain fish species that can be safely kept with each glofish species. 

Here’s a comprehensive guide that lists compatible tankmates for all 5 glofish species. 

Related: What Fish Can Live With Glofish?

Glofish bettas cannot be kept with fin-nippers like barbs, tetras, and danios. They’ll constantly nip your betta’s fins, injure it, expose it to infections, and potentially cut its life short. 

Likewise, glofish sharks shouldn’t be kept with other aggressive bottom-dwellers. It will immensely stress them out. And by now, you already know how stress can impact their lifespan. 

And glofish danios, tetras, and barbs should never be placed with big, aggressive fish that can easily gobble them up whole. 

Fish can easily swim away or hide from the bullies in the wild. But that’s not the case for captive-bred glofish. 

Before you buy new tankmates for your glofish betta, always research their compatibility first. 

Your Feeding Style Is Wrong 

Ideally, you should give your glofish 2 meals every day – an amount they can finish within 3-5 minutes. 

Unfortunately, overfeeding and underfeeding are the most common mistakes that we make in the hobby. 

First, let’s talk about overfeeding. 

When I first dabbled in the hobby, I was amazed to know how little a fish actually needs to eat. 

For instance, did you know a betta needs to eat just 3 to 4 pellets to be full for a day? Feeding any more than this will invite problems like obesity and constipation. 

Another huge disadvantage of overfeeding your glofish is that the water quality will degrade a lot faster. After all, whatever goes inside your glofish’s tummy must come out, right?

Also, the leftover food will decay, producing even more waste than ever. 

As a result, there will be an unnatural spike in the levels of harmful compounds like ammonia and nitrite. 

The water will become toxic in a span of a few days and can effectively kill your fish. 

Now, let’s talk about underfeeding. 

Sometimes, to keep the water clean for a longer time, we underestimate our glofish’s appetite. 

This exposes them to malnourishment and will stunt their lives. 

For instance, a lack of vitamin B suppresses a fish’s appetite and lowers its hemoglobin levels. 

And lack of calcium in the diet leads to skull deformities and increased mortality. 

If you’re interested in knowing more about how often to feed glofish in depth, I’m sure this article will be helpful. 

Related: How Often Do You Feed Glofish? Will They Explode From Overeating?

Your Tank’s Water Is Dirty 

Dirty water is a foolproof recipe for dead glofish. So the brains behind glofish strategically chose the hardiest fish out there to genetically modify and create fluorescent fish. 

However, no matter how tough they are, they still react pretty negatively to the wrong water parameters. 

As a fishkeeper, you should commit to setting aside some time every week or two to manage your aquarium. The tasks usually include wiping down the glass, siphoning the substrate, and ensuring all the equipment is working fine. 

But the most important thing you should do is perform routine water changes. Aim to replace at least 20-25% aquarium water every week. 

I know this sounds like too much, but you can do this in no time once you get the hang of it. 

Once you get an aquarium up and running, most of them don’t require that much work. 30 minutes to an hour each month is all you need to set aside. 

Likewise, it’s also equally important to test the water parameters to ensure nothing evil is brewing there. 

Ammonia and nitrate levels should be maintained at 0 PPP, while nitrite levels should be kept below 20 PPM. 

And to test the water, we rely on API’s Freshwater Master Kit and recommend you do so, too. 

Here’s a link to it: 

Water Parameters Changed Too Quickly

Sudden changes in water temperature, salinity, hardness, or pH can quite profoundly shock a fish and cause its death.

And this is precisely why you should first acclimate your glofish once you bring it home before adding it to the aquarium. 

After all, there will naturally be a huge difference between the properties of the water in the bag and the tank’s temperature. 

You should also be equally mindful about the extent of change in water parameters when performing a big water change or deep-cleaning the tank. 

Bottom line: Any shifts or changes in water parameters that your make in your glofish tank should be gradual and steady. 

Your Glofish Made A Long Journey 

Imagine walking outside on a bright sunny day, and some monster suddenly abducts you, sticks you into a tiny box, and transfers you to an outlandish location. Wouldn’t that be stressful?

That’s precisely how your glofish feel when they make the journey from the pet store to your home.

Getting netted, bagged, and transported is highly stressful for small, delicate glofish. On top of that, they are next going to be placed in a completely alien aquarium that has very different water parameters than what they’re accustomed to. 

The resultant stress can be fatal in most cases. 

Therefore, we recommend applying a drip acclimation method when introducing your glofish to a new setting. 

Your Fish Was Diseased 

Like humans, fish are prone to contracting the disease when stressed. And that’s because stress lowers their immune power. 

A healthy, happy, and stress-free fish naturally has a robust immune system. Their scales, skin, and slime coat are more than capable of fending off numerous pathogens and viruses waiting to attack your glofish. 

To put it simply, a healthy fish can fight off a disease that can instantly kill a stressed and unhealthy fish. 

And that’s why it’s crucial to once again revise the signs of stress I outlined above! 

If your glofish shows any of the following signs like white dots on the body, inflammation, ragged fins, and bloating, know that there’s something wrong with the fish’s health. 

At this point, you should really be seeking some professional advice. 

Your Glofish Was Old 

Here’s what the average lifespan for different glofish species looks like:

  • Glofish Tetras 3-5 years
  • Glofish Bettas 3-5 years
  • Glofish Danios 4-5 years
  • Glofish Barbs 6-7 years
  • Glofish Sharks 7-8 years 

Sometimes, fish die of old age. It’s simple. And that’s why we have included this point at last. 

To be honest, old age is least likely the correct answer behind a glofish’s death, but we still can’t rule it out. 

After all, no fish can live forever. So no matter how meticulously you care for the fish, there’s no escaping old age. 

Frequently Asked Questions 

Credit: Ho-Wen Chen (CC License)

Why Did My Glofish Die In One Day? 

Your glofish probably died within a day of bringing it home due to travel fatigue. It’s not easy being netted, packaged, and transported hundreds of miles away from ‘home’ to a completely alien environment. 

Why Did My Glofish Die Within Hours?

Your glofish most likely died within hours of bringing it home due to the acute stress it went through while being transported from the pet shop to your home. It’s not a pleasant experience at all. 

Why Did My Glofish Die After Changing Water?

If your glofish died after you performed a water change, there’s something probably wrong with the parameters. Quickly remove the rest of the fish from the tank and perform a water change. 

And once you test the parameters, fix what’s wrong with it. 

You May Also Like: How To Save Dying Fish After Water Change? Do These 6 Things!

How To Tell If Your Fish Is Dying? 

Some telltale signs that your glofish are dying are lethargy, loss of appetite, shimmies, flashing, erratic swimming, panting, and loss of balance. 

You May Also Like: What To Do When Your Fish Is Dying? Try These 5 Things!

Do Glofish Need An Air Pump?

An air pump is not as indispensable as a filter or a heater. However, your glofish can surely benefit from one. 

An air pump will ensure the water is well oxygenated at all times. And good water quality ensures good health.

Final Words: Why Did My Glofish Die?

Frankly, the answer to this question can be quite vague. 

Above, I’ve tried to list down pretty much all the possible reasons behind a glofish’s untimely death. I hope you go through them one by one and decode the reason behind your pet’s demise. 

The reasons can range from travel fatigue and failure to adapt to a new environment to parasitic infestations and acute stress. 

And sometimes, it’s just bad genetics! But, that’s not on you. 

Recommended Readings!

Can Glofish Live With Goldfish? It Can Be Costly!

How To Breed Glofish? Will You Land In Jail?

How Often Do You Feed Glofish? Will They Explode From Overeating?