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

Jan 5, 2022

How Many Glofish Tetras In A 10-Gallon Tank?

Image credits: Robert Kamalov (Creative Commons license)

I often see small tanks touted as the perfect choice for beginners dabbling in the hobby. But my friend, that’s the farthest from the truth. The biggest tank size sold for glofish is 10 gallons. And I think it’s very unmindful and misleading of the company behind glofish to sell tanks that small. So, how many glofish tetras in a 10-gallon tank would be ideal? Is it even possible?

Let’s find out. 

How Many Glofish Tetras In A 10-Gallon Tank? 

You can keep around 5-6 glofish tetras in a 10-gallon tank. 5-6 is the bare minimum number of tetras you should keep to observe their unique schooling behavior. So, you’re in luck! However, if I were to give you my two cents, I’d say go for a bigger tank. It’d genuinely make life easy for both you and the fish. 

Also, note that there are two kinds of glofish tetras available – standard and long-finned variations.

While you can safely keep 5-6 standard tetras in a 10-gallon tank, you’d have to keep fewer long-finned tetras owing to their longer bodies. 

I’d say about 4. But if you have previous hands-on experience with overstocking, you can keep around 5. 

Does The “One Inch Per Gallon” Rule Apply For Glofish Tetras?

long-finned glofish tetra
Credit: Dennis Amith (Creative Commons license)

Glofish tetras were created by genetically modifying black skirt tetras. So, they only get around 2 inches (5 cm) long in captivity. And although the “one inch per gallon” rule is debatable, the general notion is that it can still be safely applied to fish under 3 inches. 

So, even though this rule doesn’t consider the space taken by everything other than fish, the bioload, and swimming needs, the answer that it yields for glofish tetras is pretty spot on! 

As I said above, a glofish tetra’s average length is 2 inches. Therefore, a 10-gallon tank can house 5 (10/2) standard glofish tetras!

Now, let’s calculate for long-finned glofish tetras. 

Their average length is 2 ¼ inches (5.5 cm). And when we divide 10 by 2 ¼, we get 4.444. So you can either round it off to 4 or 5. 

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What’s The Minimum Recommended Tank Size For Glofish Tetras?

The absolute minimum tank size recommended for glofish tetras is 15 gallons. However, the fish in question today are incredibly active schooling fish. So, I would advise getting at least a 20-gallon long tank. If possible, go even bigger. 

Also, I really hope it’s untrue, but from what I read on forums, there’s a good chance tetras won’t school in a 10-gallon tank. 

If you’re planning on getting long-finned glofish tetras, you most definitely need to get a bigger tank as 4 fish aren’t enough to school. 

They’ll get stressed and angry. A 10-gallon tank can barely house any more than 4 long-finned glofish tetras.

Risks Of Keeping Glofish Tetras In A 10-Gallon Tank 

Small tanks are far more difficult to keep than their bigger counterparts. They practically offer no room for errors, leading to unsolicited stress and aggression. These, in turn, impact the fish profoundly by possibly stunting their growth, exposing them to diseases, and cutting their lives short. 

The fact that the biggest tank size available for glofish is 10 gallons shows that the company behind them is actively pushing the narrative that these fish are suited for smaller tanks – making them even more appealing to small, inexperienced children who will knowingly or unknowingly mistreat the fish. 

For instance, the official GloFish website states that you can safely keep two danios per gallon of tank space. That’s a stretch even by the ‘one inch per gallon’ standard. 

The good thing about small tanks is that the monetary and spatial investments are small – practically anyone can keep them anywhere. 

But there are one too many caveats that come attached. That’s why I always recommend getting the largest possible tank. 

Below, I will shed some light on the risks of keeping glofish tetras in a 10-gallon tank.

Small Room For Errors 

The biggest drawback of small tanks is that problems occur swiftly and leave devastating impacts. Mistakes often prove fatal before you even have the chance of correcting them. And that’s because of the small volume of water present.

The changes in water chemistry and temperature can happen in a few minutes. And even the slightest fluctuation in one corner can be felt throughout the tank. 

To give you an example, the same amount of ammonia in a small tank can quickly poison the whole environment, while it can dilute without any major consequences in a big tank. 

In essence, what I am trying to say is that small tanks are more challenging to maintain. It’s like walking on eggshells. You will constantly have to be on your toes to keep the water parameters in check. 

It’s going to be stressful. 

Possibly Stunted Growth 

A small tank comes with a slew of disadvantages that directly or indirectly stunt a fish’s growth. 

For starters, small tanks mean less room for exercise. Glofish tetras are super energetic fish that require sizable swimming space. If their physical movement is restrained, it’s naturally going to impact their growth. 

Second, small tanks give rise to stress and pollute water quicker. And both these factors can very well wear down a fish’s immunity and expose it to a plethora of pathogens waiting to strike. And naturally, a diseased fish won’t grow to its full potential. 

And lastly, studies have pointed out that fish leach certain chemicals into the water that stunts the growth of other fish. While research focused exclusively on glofish tetras is yet to be done, this is definitely something to contemplate. Food for thought. 

Territorial Aggression 

Glofish tetras are amicable and social fish for the most part. In fact, they get lonely and stressed if kept alone. However, if you keep too many of them cramped in a small tank, they will turn on each other. 

The lack of space to swim around freely and claim little territories will make the fish anxious and agitated – especially the males. As a result, they will resort to mean antics like nipping fins, pushing around, and relentless chasing. 

Timid individuals will have difficulty adjusting and live in constant fear of being bullied. 

Shortened Lifespan 

All the pointers mentioned above can single-handedly or collectively stress a fish and expose it to secondary illnesses. This, in turn, will degrade its quality of life and potentially shorten its lifespan dramatically. 

Fish kept in small tanks throughout their lives can contract stunted growth, spinal deformities, atrophied muscles, and other developmental health complications. 

And these conditions obviously carry the potential of killing your fish prematurely. 

Frequently Asked Questions 

glofish tetra
Credit: Dennis Amith (Creative Commons license)

How Big Is A 10-Gallon Tank?

A 10-gallon fish tank’s dimensions would be 20” (L) x 10” (W) x 12” (H). When empty, it weighs around 11 lbs. When filled, the weight increased by ten folds – reaching 111 lbs. 

How Many Glofish Tetras In A 1.5-Gallon Tank?

Sorry, but you can keep exactly 0 glofish tetras in a 1.5-gallon tank. A tank that small has too little water volume for even the smallest fish to swim comfortably. 

It also won’t be able to dilute the continual ammonia the fish will produce. 

How Many Glofish Tetras In A 5-Gallon Tank?

Technically, you can keep 2-3 glofish tetras in a 5-gallon tank, but I can guarantee that your fish will lead an unhappy and impoverished life.

Glofish tetras have an innate need to live in groups and school together. And you’d be depriving them of their basic instinct if you keep just a couple of them in a 5-gallon tank. You wouldn’t want that, would you?

How Many Glofish Tetras In A 20-Gallon Tank?

You can add 8-10 glofish tetras in a 20-gallon tank. And while you’re at it, get a long tank. These fish love to swim laps. They’d definitely appreciate the horizontal space more than the vertical. 

How Many Glofish Tetras In A 30-Gallon Tank?

You can add around 12-15 glofish tetras in a 30-gallon tank. Hobbyists on different forums recommend you can push it to 18 if you are well-versed in overstocking. 

How Many Glofish Tetras In A 40-Gallon Tank?

A 40-gallon tank can easily house 18-20 glofish tetras. It’s the perfectly sized tank for these fish to school and dart around. 

Final Words: How Many Glofish Tetras In A 10-Gallon Tank? 

Technically, you can keep 5-6 glofish standard glofish tetras and 4-5 long-finned glofish tetras in a 10-gallon tank. 

But my advice here would be to get a 20-gallon long tank as glofish tetras are active schooling fish constantly on the move. 

With all the drawbacks of small tanks mentioned above, I bet you’ll rethink your decision long and hard before settling for a small 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.