How Long Can Glofish Go Without Food? Which Species Can Go The Longest?

Dec 27, 2021

How Long Can Glofish Go Without Food

The scientists behind glofish chose the hardiest species like danios and bettas to create these genetically modified fish. Therefore, the glofish we know and adore are pretty forgiving of a beginner’s mistake. There won’t be grave repercussions for the most part, even if your feeding style is incorrect or you starve them. But how long is too long? How long can glofish go without food?

Let’s find out. 

How Long Can Glofish Go Without Food? 

Glofish tetras, sharks, and barbs can go without food for 1-3 weeks. Glofish tetra bettas can survive for 10-14 days, while glofish danios can last for up to 2 weeks. 

Except for the bright disposition, glofish are your regular fish. So, it’s always wise to look into the diet recommended for the original species before jumping to conclusions. 

How Long Can Glofish Tetras Go Without Food?

Glofish tetras are made from black skirt tetras. So, they can go without food for 1-3 weeks if they are fed small meals several times a day leading up to starvation. 

If your tank has a normal setup, glofish tetras can go without food for a week or so. But if it’s a planted tank, they can easily survive for up to 3 weeks! 

How Long Can Glofish Danios Go Without Food?

Glofish danios are produced from extremely hardy zebra danios that have a much higher fasting tolerance compared to other species. So, they can go without any food for around 2 weeks!

A healthy glofish danio has enough body mass and fat reserves to carry on the bodily functions even without food. 

However, if you starve them for any longer than that, things can go south pretty quickly – malnutrition, sickness, and even death! 

How Long Can Glofish Bettas Go Without Food?

Bettas are highly hardy – the reason they’re so popular with beginners. So, glofish bettas can survive without food for 10-14 days, provided that the tank is already established and has some extent of organic food.

However, during this period, your glofish betta’s body will switch to starvation mode and use its fat reserves to sustain. 

Naturally, there will be heightened risks of diseases. 

How Long Can Glofish Barbs Go Without Food?

A healthy, adult glofish barb, originally tiger barb, can go without food for 1-3 weeks without any hiccups. These fish are quite robust and can handle starvation pretty well.

In an aquarium, an adult glofish barb will have enough body mass and fat reserves to fast for prolonged durations once in a while.

A hobbyist on a forum commented that he regularly fasts his barbs for a week or so while he’s been on vacation for years now. 

So far, he hasn’t encountered any problems. 

How Long Can Glofish Sharks Go Without Food?

Like most tropical fish, glofish sharks can live without food for anywhere between 1-3 weeks. The tank’s size and setup, as well as the fish’s age and health, determine how long they can fast. 

Glofish sharks are created from hardy and a little feisty rainbow sharks. So, you can expect them to be fit as a fiddle. 

But note that fasting for prolonged periods can invite health complications and possibly death. 

The main query is answered. But I’d advise you to take the above suggestions with a pinch of salt. 

Even though I consulted with fellow hobbyists and looked into my own experience, these are ballpark figures at the end of the day. 

The exact duration of how long your glofish can go without food depends on several variables. Let me quickly go through them below. 

6 Factors That Determine How Long Your Glofish Can Go Without Food

Credits: Sclereid (Creative Commons license)

The five determining factors behind the length glofish can go without food are:

  • Glofish’s metabolism
  • Glofish’s diet pattern
  • Glofish’s body mass 
  • Glofish’s age 
  • Water temperature 
  • Lighting duration 

Glofish’s Metabolism

The most crucial factor affecting a glofish’s fast duration is its metabolism. Smaller fish, like tetras and danios, are very active. They usually have a pretty fast metabolism than slower, larger fish. 

As you already know, small, schooling fish like tetras and danios love to dart around, nip one another, and explore their home endlessly. 

So, naturally, these fish burn their food faster than others. 

Glofish’s Diet Pattern

Is your fish’s diet primarily plant-based or meat-based? This is another crucial factor to consider. Plants may be abundant, but they’re often low in nutrition. 

This is the reason you see herbivores graze continually. Basically, herbivore fish need to consume large amounts and more frequently to maintain their body weight. 

On the other hand, carnivore fish like bettas can eat a single meal and utilize it sporadically for long durations without eating. 

They’ve evolved to do so. They must go on for days without food in the wild due to a failed prey hunt. Therefore, they’re naturally built to endure long periods without food. 

Glofish’s Body Mass 

Considering body mass is just as crucial as metabolism, if not more. For many fish, these two variables are closely related. 

Generally speaking, bigger fish have a slower metabolism than smaller fish. They also have enough body mass and fat reserves to use when starving. 

That being said, big fish also need more food than small ones to maintain their body weight – so it’s basically a trade-off. 

All in all, the rule of thumb is that the larger the fish, the longer it can go between meals. 

Glofish’s Age 

Older glofish have higher body mass and fat reserves and lower metabolism. So, these factors collectively help them go for longer without food. 

On the other hand, young fish have a speedy metabolism. Naturally, their body weight will be low, and they have smaller fat reserves. Therefore, they’re more prone to starvation. 

Water Temperature 

Warm temperature fuels metabolism. So, the fish get hungry faster. 

While fish like danios can be kept at room temperature or cool water, lack of warmth can effectively kill bettas. 

So, lowering the temperature too fast for the fish isn’t always a good idea. 

Still, hobbyists often lower the temperature slightly if their fish have to go for long periods without food. 

If you plan to do so too, make sure you don’t lower it by more than 2 degrees. Also, make sure the change is gradual. 

If the water is too cold, it will now only slow down your fish’s metabolism but also make it sluggish and compromise its immune system.

Lighting Duration 

Fish are diurnal creatures. As the night falls, they lower their activity and prepare their bodies for a good night’s sleep. 

So, shortening the length of daylight can help limit the activity levels that would otherwise increase the need for fish food. 

For example, you can set the light timer to 6 to 8 hours instead of 12.

Recommended Readings!

How Big Do Glofish Get? What Tank Size Do They Need?

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

How Long Do Glofish Live? Which Glofish Species Lives Longest?

How To Keep Your Glofish Fed During A Holiday?

In some instances, when you have very young or small glofish, you will have to make specific provisions to keep them fed when you’re gone. The situation will get even more complicated if your glofish have special dietary needs, like newly hatched brine shrimp. 

So, here’s a list of ways you can keep your fish fed even when you’re away:

  • Automatic fish feeder 
  • Fish sitters 
  • Food blocks 

Automatic Fish Feeder 

I use automatic fish feeders if I have to be away for my work. These devices are designed to store prepared foods in a hopper and can be programmed to dispense when you want. 

The best part is you can customize the feeding frequency and size. 

If you plan to use an automatic feeder as well, I strongly suggest that you get on a few days beforehand and work your way with the system. You need to ensure if it will operate smoothly or not. 

Also, note that some automatic fish feeders are designed to dispense only a single type of prepared food, like pellets or flakes. So, make your purchase carefully. 

Here’s a link to the one I use by Torlam:

I like this particular model because it comes with a host of additional options to ensure flexible operation. 

You can calibrate it to give double or even triple feeding at specific times of the day. 

For instance, you can customize it to dispense triple feeding at noon for the entire community and a small, single serving of pellets at night for the plecos.

Fish Sitters

Fish sitters come in different forms. They can be your neighbor’s kid wanting to cash in some extra pocket money, a relative, or a friend. 

And irrespective of who you’ve chosen for this esteemed job, how well your fish fare depends on how well you have prepared them for the job. 

You must make things as simple as possible for your fish sitter. Don’t ask the person to hatch and harvest brine shrimp or refill your canister. 

Clearly specify how much and when to feed the fish. And tell them strictly not to fall for the fish’s cute begging antics even when they’re full. 

Fish sitters can also do many things automatic feeders can’t do. For instance, they can remove the fish that have died in your absence. 

Otherwise, the dead fish would rot, pollute the water, and invite other complications. 

Food Blocks 

Food blocks can be your savior if you cannot arrange a fish sitter or automatic fish feeder.

I admit they look shady right off the bat, but they have been around for decades. Plus, they’re super economical. 

They can last for a good few weeks and don’t require calibration or directions on how to operate.

Food blocks are basically mineralized blocks of animal and vegetable protein. The mineral powder slowly releases the nutrients into the water. 

While this is an ingenious idea, the caveat is that the release is constant.

So, frankly, it’s better than nothing but far from ideal! 

Final Words: How Long Can Glofish Go Without Food?

The answer to how long glofish can go without food differs from species to species. 

Glofish barbs, sharks, and tetras can survive without food for 1-3 weeks. On the other hand, glofish bettas can go on for 10-14 days, and glofish danios can make it up to 2 weeks. 

However, as I said above, these are ballpark figures. As a matter of fact, the answer will differ from fish to fish. 

The fish’s size, age, health, activity level, and environment are crucial in determining the fasting duration.

Recommended Readings!

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

How Big Do Glofish Tetras Get? Grow Them Fast!

What Do Glofish Eggs Look Like? Photos And Videos!

How Many Glofish In A 3-Gallon Tank? Zero!

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.