How Many Glofish Per Gallon? Answers For 1.5 Gallons to 55 Gallons!

Feb 10, 2022

How Many Glofish Per Gallon?

So, how many glofish per gallon? I wish I could give you a one-sentence answer. It’d save both of us a lot of time. But unfortunately, this question is so vague that I have a feeling this article will at least be 2000 words long. 

See, the catch here is that glofish doesn’t include one single species like many believe. As of now, there are 5 different species of them! 

All the answers on glofish I found on the internet focused on just glofish danios as they were the OG glofish. Now imagine applying an answer meant for glofish danios on glofish sharks. 

That’d be something, right?

Okay, enough bluff. Let’s cut to the chase now. 

How Many Glofish Per Gallon? 

Glofish tetra in fish tank

For smaller glofish species like glofish barbs, danios, and tetras, we can safely apply the debatable “one inch per gallon” rule. However, the minimum recommended tank size for a single betta is 5 gallons and for a glofish shark is 55 gallons! 

The brains behind these fluorescent fish chose the hardiest aquarium fish species available out there to create glofish. 

However, most of them differ from each other in numerous ways, and the need for space is one of them. 

While glofish bettas are often kept in 1.5-gallon tanks (which I completely detest), glofish sharks at least need 50 gallons of space each, owing to their highly territorial nature. 

Now that the main query is answered, look at how many glofish from different species can go inside different-sized tanks. Let’s begin with 1.5 gallons!

How Many Glofish In A 1.5-Gallon Tank? 

I know tetras and bettas often make appearances in lists featuring fish suitable for tanks sized 1-gallon or so. I’m really very sorry to burst your bubble, but you can keep exactly 0 glofish in a 1.5-gallon tank. 

Even if we apply the “one gallon per inch” rule, you still cannot keep any of the glofish species in a tank that small. And if you do, do your fish a favor and transfer it to a bigger home. 

It’s true some glofish species will easily fit inside a 1.5-gallon tank. But it’s even truer that the fish will lead an impoverished and unhappy life. 

How Many Glofish In A 2.5 Gallon Tank?

Sorry, but you cannot keep glofish in a 2.5-gallon tank for several reasons. 

First, the minimum recommended tank sizes for glofish bettas and sharks are 5 and 50 gallons, respectively. Second, even if you could fit some glofish barbs, danios, and tetras in a 2.5-gallon tank, it’s not recommended as these are schooling fish that should at least be kept in groups of 6. 

How Many Glofish In A 3 Gallon Tank?

By now, I think you know the drill! 

Although you can fit a couple of fish from certain glofish species in a 3-gallon tank, it’s not recommended. That’s because the fish in question are schooling fish. They feel comfortable and thrive in large numbers. And to put it simply, a 3-gallon tank doesn’t have enough space to house 5-6 of them. 

Find out what other hobbyists have to say about keeping glofish in a 3-gallon tank!

How Many Glofish In A 5-Gallon Tank? 

You can keep exactly 1 glofish betta in a 5-gallon tank. I know bettas are often kept in tanks a lot smaller than 5 gallons, but in my experience, the fish needs at least 5 gallons to lead a comfortable life. 

As for other glofish species – barbs, tetras, danios, and sharks – 5 gallons is still not a size big enough to house them comfortably. 

Technically, you can keep maybe 2 glofish danios and tetras in a 10-gallon tank, but since they’re schooling fish – it’s not really recommended. 

There are so many caveats to keeping fish in small tanks. These fish were born to dwell and forage in majestic water bodies. If we are to keep them confined in glass tanks, the least we can do is provide them with ample space – don’t you think so?

Find out what other hobbyists have to say about keeping glofish danios in a 5-gallon tank!

How Many Glofish In A 10-Gallon Tank?

You can keep 5-6 glofish tetras and 4-5 glofish danios in a 10-gallon tank. Not together, of course! 

As a matter of fact, 10 gallons is not even the minimum recommended tank size for any of these fish. 

So, even though you can fit 4-6 of them in a 10-gallon tank, it would most probably give rise to aggression problems, cause unsolicited stress, and make the water foul in no time. 

This is especially true for active fish like danios that need to constantly dart around the tank throughout the day. 

You could also house 2 female bettas in a 10-gallon tank. And if you’re toying with the thought of keeping 2 males, forget about it this instance! 

It’s a big risk to keep 2 male bettas in a single tank, no matter how big it is. But if you’re really bent over backward to house 2 males, I’d suggest getting a tank divider. 

Here’s a link to one on Amazon. You can choose the divider’s size accordingly. 

Related Articles!

How Many Glofish In A 10-Gallon Tank? Zero?

How Many Glofish Tetras In A 10-Gallon Tank? There’s Bad News!

How Many Glofish Danios In A 10-Gallon Tank? 5 Or None?

How Many Glofish In A 20-Gallon Tank?

Except for glofish sharks, the rest of the glofish species are eligible to be kept in a 20-gallon tank. If it were a species-specific tank, you could add 8-10 glofish tetras, 10-12 glofish danios, 5-6 glofish barbs, and 4-6 female glofish bettas. 

The official GloFish website reports that the minimum recommended tank size for glofish sharks is 20 gallons. So if we were to follow this, we’d be able to keep 1 glofish shark in a 10-gallon tank. 

But that claim is a far cry from the truth. No, glofish sharks cannot be kept in a 20-gallon tank. Any experienced fishkeeper will tell you that 20 gallons are simply not enough. 

The misinformation that the GloFish site is spreading isn’t sitting well with me! 

Related Article: How Many Glofish In A 20-Gallon Tank? Honest Answers!

How Many Glofish In A 30-Gallon Tank?

A 30-gallon tank doesn’t have enough space to house glofish sharks. However, you can easily keep around 12-15 glofish tetras, 14-15 glofish danios, 9-10 glofish barbs, and 4-6 female glofish bettas in a 30-gallon tank. 

In my opinion, 30 gallons would be the ideal tank size to observe the unique schooling behavior of fish like barbs, tetras, and danios. 

As these fish have an innate need and instinct to school, you shouldn’t deprive them of it. 

Plus, 30 gallons is not too big to be overwhelming to manage, nor is it too small to offer no room for mistakes. 

Related Article: How Many Glofish In A 30-Gallon Tank? Answers For All 5 Species!

How Many Glofish In A 40-Gallon Tank? 

You can keep plenty of glofish in a 40-gallon tank, but not glofish sharks. If it were a species-specific tank, you could keep about 18-20 tetras, 20 danios, 12-13 barbs, and 8 female bettas in a 40-gallon tank. 

It’d be quite a fantastic sight to behold, don’t you think?

How Many Glofish In A 55-Gallon Tank?

Finally, a tank fit for rainbow sharks! You can fit precisely 1 rainbow shark in a 55-gallon tank owing to their super aggressive and territorial demeanor. As for the rest of the glofish kinds, you can keep 25-28 tetras and danios, 18-20 barbs, and 10-12 female bettas in a 55-gallon tank. Not together, though – you already know!

Now that I’ve answered the queries for some of the most popular tank sizes, let’s have a look at what’s actually the minimum recommended tank size for these fluorescent fish. 

Let’s begin! 

Credit: Ho-Wen Chen (CC License)

Glofish are petite fish that only grow around 2 inches long – just like their original counterparts, zebra danios. Although small, these are highly active fish. 

Hobbyists recommend 10 gallons as the minimum recommended tank size for glofish danios. But I would highly recommend getting a tank bigger than that. 

That’s because the fish in question here is super active and athletic. They love to dart around the tank all day long. Plus, they’re schooling fish. 

And that’s why you should get a long tank for these fish to facilitate their endless swimming laps. 

Credit: Robert Kamalov (CC License)

Glofish tetras are made by genetically modifying black skirt tetras. Therefore, they grow around 2-2.5 inches long. Hobbyists recommend at least 15 gallons as the minimum recommended tank size for glofish tetras. 

But once again, these are extremely active schooling fish. So personally, I’d recommend getting a 20-gallon long tank or going even bigger if possible. 

Glofish barbs’ forebears are tiger barbs, and they’re just as feisty as the original species. And although they only grow around 3 inches long, they still need a big tank owing to their big personalities. 

For glofish barbs, the minimum recommended tank size is 20 gallons. But many experienced hobbyists recommend keeping them in at least a 30-gallon tank. 

You need to keep in mind that glofish barbs, too, are schooling fish. If kept in smaller numbers, they tend to become aggressive. 

Bettas are often subjected to tanks as small as 1-gallon. And that’s downright cruel. For glofish bettas, the minimum recommended tank size is 2.5-gallon. 

But I’d strongly suggest allocating at least 5 gallons for each glofish betta. This way, the fish will have plenty of room to swim around and occasionally hide to recharge its batteries. 

And when it comes to keeping two male bettas together, there’s no one magic number to decide what size tank the fish need.

Male bettas are even known to chase and fight their own reflection. Therefore, if you plan to keep more than 1 male betta in the tank, the safest bet here would be to use a tank divider. 

That’s because even if you include numerous hiding spots in the tank, there’s always a good chance the males will confront and fight until one’s down. 

On the official GloFish website, the recommended tank size for glofish sharks is 20 gallons. But that’s misinformation at its finest. Any experienced hobbyist would tell you the bare minimum requirement for a single glofish shark is 50 gallons. 

Yes, you read that right! 50 gallons. 

Just like their non-modified counterparts, rainbow sharks – glofish sharks are extremely territorial. They do not mind fighting to the death if they feel their territory is being encroached on. 

And that’s also the reason you should never house 2 rainbow sharks together in the same space, no matter how big the tank is. The alpha fish will easily bully the subdominant fish to death. 

Although rainbow sharks are not schooling fish, the minimum recommended number to keep them in is 5. 

This way, the aggression of the alpha shark is spread out. As a result, there won’t be just one fish bearing the brunt of the alpha male’s aggression. 

The Risks Of Keeping Glofish In Small Tanks 

I was baffled to know the biggest tank size advertised on the official GloFish site is 10 gallons! Their tanks start from 1.5 gallons and are available in 3-gallon, 5-gallon, and 10-gallon kits. 

I was really disappointed. I don’t understand the logic behind advertising tanks sized 1.5 or 3 gallons when you’re selling either schooling fish or extremely aggressive fish. 

GloFish brand has gone to great lengths to position these fish as beginner-friendly species that are very much suitable for children. And while it’s true glofish are made from the hardiest species available in the trade, the tank size the company recommends for them is not correct under any circumstances. 

Below, I will list some risks of keeping glofish in small tanks.

  • Small tanks offer no room for mistakes 
  • Small tanks can cause stunted growth 
  • Small tanks give rise to aggression 
  • Small tanks can shorten fish’s lifespan 

Small Tanks Offer No Room For Mistakes 

There’s a strong misconception that small tanks are easier to look after. They’re suitable for those dabbling in the hobby for the first time. However, this is the farthest from the truth. Small tanks are more challenging to manage than bigger ones by manifolds. 

For instance, even the slightest change in the water’s quality or parameter in one corner of the tank can be felt throughout the entire tank in no time. 

Second, small tanks are volatile. The parameters can go haywire with even the slightest inconvenience. There’s practically no room for mistakes. 

And lastly, small tanks will keep you on your toes all the time. You’ll need to dedicate more time than you’d anticipate keeping the parameters healthy and perfect. More frequent water changes, tests, cleaning, and so on and so forth. 

Small Tanks Can Cause Stunted Growth

There’s another popular misconception that fish grow to the size of their tanks. While there’s no scientific backing behind this famous claim, we cannot rule out that small tanks stunt the fish’s growth. And it does so in numerous ways. 

For starters, small tanks don’t offer enough room for exercise. So, your fish won’t get to stretch its muscles as much as it’d like. This would feel like a punishment for active fish like danios and barbs that need to swim around constantly. So, we can say that lack of exercise can potentially stunt development, right?

Next, small tanks get polluted quickly. There are also going to be frequent duels about the territory. Both these factors are more than capable of profusely stressing your fish. 

And when a fish is stressed, its body fails to properly produce white blood cells – thus, compromising the fish’s immunity. And unhealthy fish don’t grow to their full-size potential, do they?

And finally, studies have shown that fish release specific pheromones into the water that hinder the growth of other fish. In a small, closed system like aquariums, these chemicals won’t have anywhere else to go and will end up being absorbed into the fish’s body. That’s a matter of great concern for me! 

Small Tanks Give Rise To Aggression

We like to think of fish as mindless and primitive animals who, at best, can be show ponies. But it’s untrue. Fish can feel a wide range of emotions – and stress and aggression are two of them. 

When there’s not enough space in the tank, the fish are inevitably going to fight over who gets to claim what part. So, naturally, the alphas will claim most of the tank and swim around freely, while the subdued fish will be forced to cower in the corner. 

This will cause immense stress to subdued fish. And you already know what stress does to their body, right? 

Small Tanks Can Shorten Fish’s Lifespan 

All 3 pointers listed above can collectively or single-handedly stress your fish and mess with its health status. Disease can cut a fish’s life – that’s obvious – you already know that. 

But stress too can profoundly compromise a fish’s life. A fish that’s constantly living in fear or agitation isn’t going to be healthy. All the emotions the fish is experiencing will ultimately take a toll on its health and compromise its lifespan. 

Final Words: How Many Glofish Per Gallon?

There’s no magic formula or one golden rule to answer how many glofish per gallon you can safely add. 

Glofish come in 5 different varieties, from 2-inch-long danios to 6-inch-long sharks. Therefore, we cannot come to a single conclusion for an answer. 

For glofish species smaller than 3 inches – like danios, barbs, and tetras – you can safely apply the “one inch per gallon” rule. However, all 3 of them are schooling species and shouldn’t be kept in numbers smaller than 6. 

Therefore, I’d suggest keeping them in a 20-gallon tank at least. But, of course, bigger is always better.

I’d recommend allocating at least 5 gallons each for bettas, although I know they’re subjected to tanks a lot smaller than that. 

And lastly, you will need to provide 50 gallons of tank space as the bare minimum for a single glofish shark. And it’s never ever a good idea to add more than 1 shark in the same tank. 

These fish are extremely territorial and aggressive. They will not tolerate the presence of other fish of the same species or anyone that remotely looks like them. 

Recommended Readings!

Why Did My Glofish Die? One Too Many Mistakes!

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?

Do Glofish Need Light At Night? Blue Light Harms Their Eyes?

What Glofish Can Live Together? 2022 Compatibility Guide

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.