How Many Days Can I Fast My Betta Fish?- What’s Too Long?

Planning to leave your Betta alone for a few days? No worries, Bettas don’t react to fasting adversely. You can easily leave the house for a few days without worrying about an urgent fish-sitter. But how long is too Long? There must be a limit to how long your Bettas can tolerate living without food, right?

You can let your Betta fish fast for one to two weeks. That’s a broad range. The ideal range is 3 to 5 days because it doesn’t have any negative impact on the Betta. However, prolonged fasting, like 12-14 days, can cause immense stress for the betta fish.

That’s a pretty straightforward approach. But as a Betta-lover, you should know how your pet is going to react day by day after the fasting starts. That’s exactly what we will be doing in today’s article. Keep reading to find out.

Key Takeaways

  • Bettas can easily stay without food for 3-5 days without feeling starved.
  • One week is the end of the safe zone. You must run a water change (at least 80%) before starting the fast.
  • 10-14 days long fasting is considered hazardous.
  • After 6 days, the fish starts showing signs of lethargy to store energy.
  • Don’t overfeed the fish afterward to compensate for the fast.
teal red white color betta
Owner: Frankie Hernandez

How Many Days Can I Fast My Betta Fish?

One problem with fish-keeping is that you can’t bring your pets with you everywhere. Sometimes when you are staying out, you just have to leave your Bettas at home by themselves. In that case, how many days can you fast a Betta fish? Let’s check out.

Number of daysTemperamentHunger LevelStress LevelNoticeable Health IssueWater Change
Day-1Peaceful and calmzeroWithin ideal rangeNo health issueNot necessary
Day-2Peaceful and calmzeroWithin ideal rangeNo health issueNot necessary
Day-3Peaceful and calmzeroWithin ideal rangeNo health issueNot necessary
Day-4A little restlessFeels a little starvedIncreased a littleNo health issueRequired
Day-5A little restlessFeels a little starvedIncreased a littleNo health issueRequired
Day-6Become aggressiveFeels starvedActs weird due to stressStarts swimming less, hides more.Required
Day-7Become aggressiveIncreased hunger pangsActs weird due to stressTriggered lethargy, swims less.Mandatory
Day-8Starts panickingIncreased hunger pangsHighly stressedTriggered lethargy, swims less.Mandatory
Day-9Limits movement, avoid other fish.Might go into hibernationHighly stressedLethargy, constipation, skin discoloration.Mandatory
Day-10Limits movement, avoid other fish.Might go into hibernationHighly stressedLethargy, constipation, skin discoloration.Mandatory

Day 1-3: Perfectly safe

So, the first three days are called the “safe” zone. You can let a Betta fish fast for one, two, or three days in a row, and we promise there won’t be any noticeable issues. As far as health is concerned, experts often suggest fasting overfeeding too much.

See also  Do Bettas Eat Snails? Why?

The main logic is that Bettas living in the wild don’t get to eat frozen bloodworms, mosquito larvae, and Brine shrimp daily. They get some meat on a lucky day and store the nutrition (mostly fat) in their body till their next catch. And, if you compare the fitness level, the wild ones are in a better condition than your pet. That explains why you should let your Betta fast from time to time as well. It will bring their eating routine close to what’s considered natural.

Reports also suggest that it’s best to let your Bettas fast for two to three days if you have changed the tank set-up recently. It helps the fish have enough time to adjust to the surroundings and water parameters. Fish keepers often worry when their Bettas refuse to eat properly after a tank change. Now, you know there’s nothing to worry about. Not eating for a few days is perfectly normal and even healthy for your Betta.

What Kind Of Water To Use For Betta Fish

Day 4-5: Safe But Requires Care

For the first three days, you had no mandatory job. Water change is not necessary as well. But as you extend the fasting period up to 5 days, things get a little hard. Your Betta is still not feeling the impact of fasting (not that much). It might go up and look for food because of habit, but it would be just fine. There is also no noticeable change in their behavior. You will see them getting along with the tank mates and even flaring their fins.

But we recommend you consider the tank size. If you have kept your Betta in a 2-2.5 gallon tank, it will get dirty pretty easily. Since the fish have been hungry for so long, they might mistake the waste for food and start intaking toxins. You should definitely change the water in this time period.

Make sure the water temperature, pH level, and oxygen level are within the ideal range to not increase the Betta’s stress while fasting. And, if you are unable to stay home for a water change, shift the fish to a bigger tank. A 5-gallon aquarium should be enough.

Day 6-8: Becomes Lethargic

Lethargy means not moving much and becoming lazy. It’s not a good thing for Bettas in normal circumstances. But during a fasting cycle, Lethargy can act positively for pets. For example, you want the Bettas to not feel starved or stressed. It happens when there is enough energy stored in the body already.

See also  How To Increase Betta Fry Survival Rate?

And guess what? Swimming up and down consumes all the energy your Betta has stored inside its body. So, the chances of surviving till the end of the fasting cycle get thinner. However, once the fish starts showing signs of lethargy, it’s a relief. Because now the Betta won’t waste its energy on useless daily activities. It hides behind rocks or leaves and pretty much stops moving to save as much energy as possible for the next day. having enough energy also lowers the stress level.

One small tip is to decrease the water temperature by a few degrees (72 degrees Fahrenheit). The cooler temperature impacts the Betta by cooling down the body temperature as well. Hence, the metabolism procedure slows down. That means the fat stored in Betta’s body will burn very slowly. It helps the fish get through such a one-week-long fasting ritual without getting hurt.

Don’t get afraid if you find your fish in a lethargic (looks like it’s dead) mode. It might eat all the food and still stay lazy. Just be patient and keep offering appropriate portions of pellets. Your betta will soon bounce back and move out of the lethargy zone.

betta fish eating
Owner: Frankie Hernandez

Day 8-10: Starved and Stressed

You are just on the edge of ruining your Betta’s metabolic system. Usually, 1 week is enough to burn the majority of the fat stored inside your Betta. They slowly start to feel starved, and it hikes up their stress level. You will notice them swimming up and down, frequently searching for food. Lack of food can trigger lethargy (laziness, reduced overall activity).

If it’s matured Betta (2+ years), there would be more fat stored in its body. That helps when it comes to longer fasting periods. On the contrary, a young Betta would feel more restless and starved during 8-10 days long fast.

If you are leaving your fish for more than a week (for 8 to 10 days), you need to appoint a fish-sitter. There’s no way your pets can survive this long without any water change. You need to clean the tank at least twice during this period. and, for a more helpful outcome, attach a filter on top of the aquariums.

Even though a filter is not mandatory for Bettas, it’s really handy when you are away from home. This small device constantly checks the water parameters and keeps the ammonia level, oxygen, and pH level in check. So, you don’t have to worry about your Bettas swimming in an inhabitable tank.

Day 10-14: Might Survive But Extremely Risky

Here comes the risky part. What if you can’t come home until 2 weeks later? Will your Betta be okay fasting for so long? Well, there’s a high chance it will survive. But we can’t say its medical condition would be the same. after one week, bettas usually stop swimming or roaming around the tank.

See also  Can Betta Fish Eat In The Dark? – Or Is It Dangerous?

It’s their coping mechanism with the new fasting cycle. They are trying to store as much energy as possible. So, you will notice the fish hiding behind leaves and literally not moving at all. But they might not be dead yet.

Some common health issues after 2 weeks long fasting include constipation, the tendency to overeat, which leads to bloating, diarrhea, etc. If your Betta is weaker, it might deal with some heart diseases due to extreme stress and panic.

In the end, we highly discourage you from leaving your Betta for 10-14 days without food. Use automatic feeders or simply appoint a fish-sitter. Make sure the water filter is running okay, and the tank is cleaned at least 50% three to four times.

What Not-To-Do While Your Betta Is Fasting

Here are our three not-to-dos while your Betta is fasting. Please take a look.

1. Don’t Overfeed Prior To Fasting

One major misconception is that a full tummy will help your Betta last longer. That’s why we see pet-owners offering two or more portions of food in one go. But let’s make this clear. You are not helping the poor fish. In fact, having too many food particles in the tank can pollute the environment. It gets cloudy and uncomfortable for your Betta.

And guess what happens when there is more food? Yes, there will be more waste as well. So, the majority of the aquarium water is filled with debris, left-over, and toxins. It’s not a good habituate for your Bettas. You will have to run a water change sooner than your schedule allows. That’s a huge hassle. So, please don’t overfeed your fish.

betta fish among colorful plants
Owner: Tony Vincent

2. Don’t Overfeed Once The Fast Ends

Just like what we have said earlier, you are not supposed to give too much food after the fasting cycle. Yes, your Betta will look stressed and sick. You might feel like it needs more portions than a normal day. But that’s a misconception. A stressed betta will gulp down every food you drop in the aquarium. It’s a survival tactic to reverse the fat loss in the body.

 But in the process, the Betta will also reverse all the benefits of fasting. Soon, you see a bloated stomach which is extremely uncomfortable and dangerous for Bettas. So, try to maintain a steady feeding portion after the fast breaks. Even though the Betta vigorously eats whatever you put in the tank, don’t get too swayed by that behavior.

3. Don’t Introduce New Tank-Mates

Bettas like to be left alone, especially when you are not giving them food. Introducing a new fish in the aquarium will be a very bad idea. Since the Betta has a higher stress level and is in a state of panic, a new fish can seem like a threat. There’s a very low chance the two will get along. Bettas also are territorial and like to dominate other species. Since you have starved them, the Bettas might feel extremely vulnerable and can get bullied by the other fish.

Before You Leave!

Nobody loves fasting their favorite pets, especially if they are as small as Bettas. But universally, letting Bettas fast is a common practice. If you are a new betta-keeper, you must be wondering why exactly do people do that? are there any benefits to letting your Betta fast? Well, you can follow our next article to find the exact answer. Hope you enjoyed it.

Article: Can I fast my betta fish?

Muntaseer Rahman

About Author

Hello, I’m Muntaseer Rahman, the owner of I’m passionate about aquarium pets like shrimps, snails, crabs, and crayfish. I’ve created this website to share my expertise and help you provide better care for these amazing pets.


This site is owned and operated by Muntaseer Rahman. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to This site also participates in other affiliate programs and is compensated for referring traffic and business to these companies.