A question that every fish owner comes across at least once is – How long can my fish live without food? Many have a pet fish in their hotel rooms or workplaces.

It is easier for furry pet owners to take their pets with them on vacations, but quite a task for fish owners. Aquariums are bulky to carry, delicate to handle (glass-made), and need an uninterrupted power supply.

Besides, it requires a little more expertise in managing fishes. Hence, you cannot leave them with anyone.

This article covers critical aspects of leaving fishes unattended without harming them, which would help most hobbyists.

How long can Fishes Go Without Food – Influencing Factors

The main concerns about leaving fish alone are feeding and maintaining water quality while you are away.

According to experts, most fishes can go without food for three to seven days and yet be healthy and alive. However, their ability to starve depends on multiple factors.

Aquarium Status and Size

A newly set up aquarium needs more attention to water quality. The aquarium ecosystem is not yet fully established. Enough good bacteria are yet to colonize, and the chances of ammonia/nitrate spike are high. Leaving such an aquarium unattended can prove fatal.

On the other hand, good bacteria in a matured aquarium set off the nitrite and ammonia build-up ongoingly. Besides, tankmates have settled with each other without any issues. So you can be assured of their well-being compared to a new aquarium.

A smaller aquarium needs more frequent water changes than a larger one/a pond. It can become a restricting factor in your absence.

Fish-based Attributes

In the wild, fishes do not always get assured food. Hence, most of them overeat to withstand lean/no food periods. Their bodies build up fat reserves that get deployed for survival when needed.

Various mouth-brooding species fast for a few weeks to almost a month while carrying their eggs/frys in their mouths, post-spawning. The female African Cichlid can starve for a month during this phase. Migratory fishes go without food for long stretches during migration.

Goby fish starve themselves to remain small-sized and thus appear less threatening to other fishes. It is their survival mechanism.

Besides, the parameters listed below directly impact any fish’s ability to go without food.


Adult fishes can go longer without food, as the fat reserves in their bodies are higher.

Younger fishes cannot face long periods with no food compared to mature fishes. Their bodies are still developing, and hence fat reserves are less.

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Fish frys need food multiple times a day in small portions. Their food is also different from adult fishes in the first two weeks. Thus, they cannot be left unattended. It will be fatal for them.


Carnivorous fishes (like Bettas, Tetras, Oscars, Pufferfish, Clown Loach, etc.) eat only when they prey successfully, when in the wild. Thus, their next meal is always uncertain. Hence, their bodies are capable of going without food for prolonged periods.

Herbivorous fishes (like Otocinclus, Tangs/Surgeonfish, Plecos, etc.) keep grazing plankton, algae, decaying matter, etc. Their food has relatively lower nutritional content and is difficult to digest. Hence, they keep eating the whole day to sustain themselves.

Thus, they cannot starve for long. At the same time, a planted aquarium reduces the much-needed concern about feeding them.

Some fishes are omnivorous (like Goldfish, Guppies, Mollies, Angelfish, Discus, Cherry Barbs, Catfish, Corydoras, etc.). They adjust their diet according to availability. Their ability to starve is relatively flexible.

Water Temperature

Higher the metabolism, the more frequent the need to eat, and vice versa.

Fishes living in cold waters (like Goldfish, Platys, Danios, Bettas, Bloodfin Tetras, Dojo Loach, Cherry Shrimp, etc.) have a slower metabolism rate than fishes in warmer waters.

Tropical fishes (like Guppies, Mollies, Bettas, Dwarf Gouramis, Swordtails, Kuhli Loach, Plecos, etc.) need warmer waters. Hence, they have a reduced ability to starve.

Below diagram shows the co-relation between water temperature and number of days fishes can go without food. Experts suggesting them have cautioned that it is not recommended to starve fishes for prolonged periods, unless unavoidable.

co-relation between water temperature and number of days fish can go without food

Adult Size

Large-sized fishes have more fat reserves than small-sized ones. Hence, they can survive food deprivation for a comparatively long time.

Activity Levels

Active fishes (like Tetras, Zebra Danios, Tiger Barb, Tangs/Surgeonfish, Green Terror, Swordtail, Clown Loach, etc.) need more food and nutrition to sustain their activity levels, compared to less active fishes.

Interspecies differences in activity also matter. Use your observation and discretion to decide how active your Swordtail (say A) is compared to Swordtail (say B). Being nocturnal does not mean being less active. Categorize accordingly.

Did you know? A study on Hoplias Malabaricus (known as wolf fish, tiger fish, guabine, or trahira) showed that they survived up to 180 days without food and regained their normal metabolism when re-fed.

Other Factors

Seasonal or sudden variations affecting the water temperatures, health of fishes, breeding seasons, and pre/post-spawning dietary needs can vary.

Is Fish Fasting Beneficial?

Most aquarium fishes are overfed. It is healthy to skip feeding them once or twice a week. It ensures optimal health/growth and avoids complications due to overfeeding (like swimbladder).

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While transporting fish for trade, they are deprived of food for a day or two before transporting. Post emptying their stomachs, they sealed in small bags with water and oxygen. It reduces/zeroes bioloads (peeing/excreting) during transit.

Hence, you may receive the fish stressed/with faded colors. But after some time, they regain colors in your aquarium.

Did you know? A study indicates that fishes deprived of food compensated for lost nutrition in their next feeding. They grew faster (compensatory growth) than fishes fed regularly. Aquacultures use fasting and re-feeding techniques for faster growth rates.

Managing Fishes While on Vacation

Pre-departure (for a 3-day vacation)

If your aquarium is well-maintained, all fishes are healthy and not ready to spawn; you can safely take a three-day unplanned trip without any concerns.

However, they will need uninterrupted filtration, oxygen, lighting, and a generator (to combat sudden power failure), whether the holiday is pre-planned/sudden.

Before a planned travel :

  • Do not perform water changes on the day of leaving. Do partial water changes at least two days before leaving.
  • Clean your filtration system of clogging, and ensure the aquarium light timer is on.
  • Give them extra feeding in small portions for two days before leaving. Do not overfeed. It will help build their fat reserves.
  • Reduce the aquarium daylight to 4 hours to shorten their day. Their activity levels will reduce, reducing the need for food.
  • Reduce the water temperature gradually by 2 degrees F daily. Do not make it unbearable for them. It will lower their metabolism rates.

Pre-departure (for more than 3 days of vacation)

Although most fishes can live without food for 3 to 7 days, it is not advisable to deprive them of food for more than three days at a stretch unless advised by a fish vet.

Besides following section 3.1, the main concern here is how to feed your fish while on vacation.

You have the following options.

Automatic Fish Feeder

Image Credit: Amazon

It is a great way to feed fishes while you are away. You need to fill the container with fish food and set the timer. It will automatically dispense the desired portion at preset timings.

All food must be dry. Avoid foods (like powder/flakes) that may clog the dispenser opening. Feed 50% of the normal portion to reduce bioloads without starving them.

There are various brands available. Buy a battery-operated automatic feeder to avoid the impact of accidental power failure.

Use the automated feeder for a few days before you leave to understand the nitty-gritty and ensure it is functioning well. Many hobbyists use it regularly to feed their fishes and are happy with their decision. Occasionally, they hand-feed them to get the bonding experience.

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Fish Food Blocks

Image Credit: Amazon

They are also known as holiday/weekend fish food blocks. They come in various brands, sizes, and shapes. Follow instructions (gallon-wise) and drop the correct number of food block(s) in the aquarium before leaving.

It keeps dissolving slowly, releasing fish food. The only issue is that the dissolution continues even after the fishes have eaten, which can contaminate the water. Besides, it is difficult for the fishes to recognize it as food. Some fishes might bite/eat it. It is harmless.

An automatic fish feeder is better than fish food blocks, as you can decide the portion, time, and type of food you wish to feed.


Finding a helpful neighbor, friend, colleague, or fellow hobbyist to help you out is a good option.

If they have no prior experience in fish-keeping, you will need to teach them about

  • How to feed fishes.
  • Performing water changes (if required). Keep replacement water ready before leaving.
  • Check if oxygen and filtration are working fine (by simple observation).

Pack date and meal/time-wise food in small sachets and label them. Remember, only 50% diet in your absence.

There are professional fish-sitters. Check with your local pet store/expert about your options. It is better to leave your aquarium at the professional fish-sitter’s place.

Leave emergency contact numbers to contact you, your fish vet, and the nearest pet store(s). Ask them to give you regular updates through video calls.

Fish-sitters can remove a dead fish, handle unforeseen power/equipment failures, or provide timely help if any fish is unwell, making them preferable.

Upon Return

  • If you have followed the above guidelines, you might return to a clean aquarium with healthy fish.
  • Reset the aquarium daylights to 6-8 hours.
  • Normalize the water temperature gradually by 2 degrees F daily.
  • Slowly increase their food intake from 50% to 100%. Sudden change will unsettle their digestive systems.

Parting Thoughts

Many experts claim that:

  • Goldfish can go without food from 3 days to months (depending on the water temperature)
  • Betta fish can live without food for 3 to 14 days.
  • Guppies can go without food for a week to 10 days.

However, all of them insist on avoiding such extreme periods of food deprivation, especially when we have options (refer to section 3.0). After all, no fish owner would like to return from a vacation to see sick/dead fish in the aquarium. Better safe than sorry.

We hope you are now ready to take that much-needed vacation. We wish you a happy vacation time!

Read here –

Can Fish Drown? Your answer is here.

About the Author

Shelby Crosby

Shelby is a passionate fishkeeper who has been writing about fish for over 5 years. She is a pro aquarist and holds a BSc Honors Degree in Wildlife and Fisheries. She creates her own beautiful aquarium layouts and loves to share her knowledge of tropical fish with other hobbyists. Career Highlights: Has worked with several…

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