How Many Glofish Danios In A 5-Gallon Tank? You Might Not Like My Answer!

Jan 2, 2022

how many glofish danios in a 5-gallon tank

Image Credit: Ho-Wen Chen (Creative Commons license)

The official glofish website states that you can ‘safely’ add two glofish danios per gallon of tank space. So, by that logic, the answer to how many glofish danios in a 5-gallon tank is 10. Does it sound too good to be true? 

It is, indeed. 

So, let me honestly tell you the number of glofish danios you can fit inside a 5-gallon tank. 

I have a feeling that you won’t like my answer, but it is what it is. 

How Many Glofish Danios In A 5-Gallon Tank? 

Unfortunately, you can keep precisely 0 glofish danios in a 5-gallon tank. If you were to follow the ‘one inch per gallon’ rule, you could technically fit 2 glofish danios that grow around 2 to 2.5 inches long in a 5-gallon tank. But it is not humane to keep glofish in a tank that small. 

The minimum recommended tank size for glofish danios is 10 gallons. Even then, I’d still suggest getting at least a 20-gallon long tank as the fish we’re talking about today are extremely active and prolific swimmers. 

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Why Shouldn’t You Keep Glofish Danios In A 5-Gallon Tank?

In short, the main reason you can’t keep glofish danios in a 5-gallon tank is because they are schooling fish that at least need to be kept in a group of 6. And as you can already guess, a 5-gallon tank can in no way accommodate half a dozen glofish danios. 

Below, I’ll explain further and list out some more reasons why it’s a bad idea to keep glofish danios in a 5-gallon tank. 

Glofish Danios Need To School 

Schooling is an innate instinct for glofish danios. It’s their second nature. So, when you keep them alone or in very small groups, they will inevitably get depressed. Yes, I am not exaggerating things here. They will get depressed and consequently stressed, which will then negatively impact their growth. 

They will even show physical symptoms like lethargy and appetite loss, leading to complications like stunted growth, infertility, weakened immune system, and heart problems. 

Another problem that stems from keeping schooling fish alone is aggression. Glofish danios have a pleasant personality for most parts, but once they get lonely, they will start lashing out at other tankmates – chasing them and nipping their fins. 

So, the bottom line here is that glofish danios should be raised at least in a group of 6, and a 5-gallon tank isn’t big enough for that. 

Your Glofish Danios Will Get Bored 

Anyone who has raised glofish danios will tell you that they are super active fish. If I dare say, these fish have an athletic disposition. They constantly love to swim around and explore. 

Their favorite pastime is to dart around the tank like a flash. And unfortunately, a 5-gallon tank simply doesn’t have enough space to accommodate glofish danios’ athletic needs. 

Your glofish danios will undoubtedly be bored witless.

These fish need a long tank with a bigger footprint to pace around. So a 15-gallon long tank would be the bare minimum requirement here. But as I always say, go for a bigger tank. 

If you’re really keen on raising glofish danios, I’d suggest getting a 20-gallon long tank as a starting point. 

Small Tanks Can Stunt Glofish Danios’ Growth

Small tanks can stunt the growth of your glofish danios in many ways. I’ll tell you how. It may seem far-fetched at first glance, but hear me out. 

As we have already established above, glofish danios are highly active fish. Naturally, therefore, they need plenty of exercise. And there’s no way they can get enough exercise in a 5-gallon tank that barely has any space to swim freely. 

Your glofish danios won’t be able to dart and pace like they’d love to. And lack of exercise can definitely be linked to stunted growth. 

Second, a small fish tank will stress your fish due to polluted water, territorial aggression, and lack of privacy. And stress will weaken your fish’s immune system as it will deplete white blood cells that help fight off infections. 

So, a diseased fish will naturally experience stunted growth, wouldn’t it?

And lastly, researches have shown that fish release certain hormones into the water that can inhibit the growth of other fish. In an enclosed system like an aquarium, this spells a problem. 

Most of these studies have been focused on fish like carps and trouts, but we cannot 100% rule out the possibility for other fish as well. 

All in all, a small and overcrowded tank is an unhealthy environment. Consequently, unhealthy fish won’t grow as well as healthy fish. 

Small Tanks Are Harder To Maintain 

Small tanks are often touted as ‘beginner-friendly’ and ‘self-maintenance’ – but that’s the farthest thing from the truth, like ever!

To put it simply, small tanks have small rooms for errors. Wait, let me rephrase that. Small tanks have no room for mistakes. Even the slightest mistake from your side is magnified – and the next thing you know, your fish is dead. 

For example, the same amount of uneaten food can wreak havoc in a small tank, whereas it can get diluted with no consequences in a bigger tank. 

With small tanks, also note that even the slightest change is felt throughout the tank. And glofish danios don’t react well to sudden and unsolicited changes. 

I really don’t understand why the company behind glofish sells tanks with a maximum capacity of 10 gallons while there are glofish species that need 50 gallons each. 

Frankly, I think only one glofish betta can happily live in a 10-gallon tank. None of the other 4 species would prefer it. 

Small Tank Will Stress Your Glofish Danios

All the points stated above, combined or single-handedly, can severely stress out your glofish danios. And as I said earlier, stress will wear down their immunity and expose them to several ailments. 

Your glofish danios may survive in a 5-gallon tank. But mark my words – they will lead an impoverished life. They will not be happy. And don’t be surprised if they die prematurely. 

We’re all guilty of overlooking our pet fish’s needs and treating them like commodities at times. 

But as mindless as we think fish are, they are intelligent beings with unique needs, capable of feeling a wide range of emotions. 

Below, I have collected some real answers from real hobbyists who have shared their opinion on keeping glofish danios in a small tank. 

This is my honest attempt to help you guys find well-rounded information in one platform. 

So, let’s see what they have to say! 

How Many Glofish Danios In A 5-Gallon Tank? Real Answers By Real People! 

glofish danios
Credit: Ho-Wen Chen (Creative Commons license)

“Glo danios, barbs, and tetras all need a big tank of at least 20 gallons capacity to swim and school.”

“Glofish danios are hyperactive schooling fish that are great to be kept at least in a group of 5 in a minimum of 10-gallon tank.”

“Zero. The only fish I would keep in a 5-gallon tank at a push is 1 betta.”

“I just can’t comprehend why they sell small glofish tanks when you can’t put any more than 2 or 3 in there together. My daughter got a glofish tank with 3 glofish recently. One of them got sick and one got eaten!”

“Sorry, but NONE of the glofish varieties are suitable for a 5-gallon tank. That company is guilty of some of the worst false advertising. All of the glofish species are very active and hyper. They need at least 30” of tank length or larger.”

“Keeping glofish danios in a 5-gallon tank is like sticking a border collie in an apartment. Your fish will go crazy and get very nippy – often to the point that the weak one will get picked to death by the dominant ones.”

“Glofish danios are active fish. That “inch per gallon” rule is stupid. These fish are crazy active. You need to provide a 20-gallon long tank, preferably. If stuck together for too long, they’ll start nipping fins.”

So, I guess the message is loud and clear. 

But before you head out, check out answers for how many glofish danios can be kept in 10, 20, and 30-gallon tanks! 

Frequently Asked Questions 

Credit: Ho-Wen Chen (Creative Commons license)

How Many Glofish Danios In A 10-Gallon Tank? 

You can keep 4-5 glofish danios in a 10-gallon tank. But I’d still recommend getting a 20-gallon tank. 

How Many Glofish Danios In A 20-Gallon Tank? 

You can keep 10-12 glofish danios in a 20-gallon tank. Watching them school and socialize would be a lovely sight to behold.

How Many Glofish Danios In A 30-Gallon Tank?

You can easily keep 14-15 glofish danios in a 30-gallon tank. If you have previous experience with overstocking, you can add a couple more. 

How Many Glofish Danios In A 40-Gallon Tank?

You can keep around 20 glofish danios in a 40-gallon tank. Your fish will have all the room they need to dart around and school in a tank that size. They’d truly be happy! 

Final Words: How Many Glofish Danios In A 5-Gallon Tank?

Take my advice with a pinch of salt, but you can fit 0 glofish danios in a 30-gallon tank. 

If we were to follow the infamous ‘one inch per rule,’ we could technically fit 2 glofish danios in a 5-gallon tank. 

But keeping just 2 of them – that too in a tank that small – is downright cruel. We don’t want our fish to suffer, do we?

Glofish are schooling fish. You should at least keep 6 of them together. And a 5-gallon tank isn’t big enough to house them all. 

The absolute minimum tank size recommended for these active fish is 10 gallons. But I’d suggest you start from a 20-gallon long tank. 

If a 5-gallon tank is the best you can do, I’d suggest keeping just one glofish betta in it. Schooling fish don’t belong in a 5-gallon tank. 

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rohit gurung author at urbanfishkeeping

About Rohit Gurung

My never-ending love and fascination with Aquascaping started when I received a red-eared turtle for my 10th birthday.

Apart from researching and writing, I spend hours gazing at my 3 turtles. And yeah, I bask alongside them too.