How Long Can Fish Go Without Food? A Helpful Guide

Alison Page

Alison Page


How Long Can Fish Go Without Food

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If you’re going away for a few days, you might wonder how long your fish can last without food.

Is it okay to leave your fish with nothing to eat for a day or two? Can fish benefit from fasting? And how can you keep your fish fed when you’re on vacation?

Read this guide to find out!

How Long Can Fish Go Without Food?

Unfortunately, there’s no straightforward, cover-all answer to that question!

In the wild environment, fish can often go without daily feedings, especially if the fish in question is a predatory carnivore. In that case, prey availability dictates how often the fish get to eat. 

The female mouth-brooding African cichlid is an extreme example of fish fasting. These fish carry baby fry in their mouths for up to a month. So, during that period, the fish go weeks without food.

However, an adult, healthy aquarium fish can generally last for three to seven days without food. Some species of pet fish can even survive a lack of food for over two weeks!

Wild and captive-kept adult fish generally have sufficient body mass and fat reserves to miss a couple of meals occasionally without coming to any harm. Omnivorous fish, including goldfish, happily graze on algae deposits within their tank between feeds.

So, if you can’t feed your fish pets for a day or so, they can survive perfectly well on what they find in their environment without needing to be fed.


Some fish species, including bettas and Fancy goldfish, benefit from one day a week without food. Expert fish keepers maintain that a weekly fasting day is crucial for preventing health issues in their fish, such as constipation and swim bladder disease.

How so?

Fancy goldfish and other round-bodied fish can become constipated if fed a diet of flaked food or pellets. When the fish is constipated, the build-up of excess food places pressure on the swim bladder, making it impossible for the fish to swim properly on an even keel.

Affected fish sometimes sink to the bottom of the tank and can’t swim back to the surface. Others might swim in circles on their sides, whereas some can become stuck at the water’s surface. Usually, fasting the fish for 24 to 48 hours is all it takes for the fish’s digestive system to clear itself and fix the problem.

You can also try offering the fish some meaty food or fresh veggies, following a day or two without food.

What About Fish Fry?

Fish fry and juvenile fish should be fed several times a day.

Young fish need additional calories to fuel healthy growth and development as well as for maintenance. If you don’t provide fry with the nutrition they need, the youngsters could suffer from deformities and will almost certainly fail to thrive. Some fry might even die if you don’t give them the necessary food.

Influential Factors On Fish Feeding Frequency

Several other factors influence how long fish can go without food.

Activity Levels

How long your fish can manage without food depends largely on the type of fish you keep and their metabolism.

For example, small fish are generally pretty active creatures, so they need more food than larger, slower fish. So, if you have an aquarium full of lively rasboras, tetras, and other active fish darting around exploring their environment and chasing each other, they will need sufficient food to fuel that activity.

These kinds of fish naturally graze on plankton, insect larvae, and the like. So, the fish enjoy small feeds throughout the day. Those fish should be fed two or three times per day in a captive environment. 

Water Temperature

Water temperature influences how long your fish can go without food.

Generally, the warmer the water, the faster your fish’s metabolism will be, and the more food the fish will need. In cooler environments, the fish’s metabolism runs more slowly, so they need less frequent feedings.

In either case, overfeeding causes your fish to become overweight, and you’ll end up wasting uneaten fish food and polluting your tank water.

Herbivores or Carnivores?

Your fish’s eating habits also determine how long the fish can go without food.

Herbivorous or omnivorous fish tend to graze continually. The plant matter these fish eat is low in energy, so they need to eat lots of it to give them the energy they need.

On the other hand, carnivorous fish can survive on a single meal before going for a longer period without eating.

What Size Are Your Fish?

The fish’s body mass is equally important as its metabolism in determining how often it needs to eat and how long it can go without food.

In general, larger fish have slower metabolisms than smaller ones. However, big fish need more food than smaller ones to maintain body weight, so that’s a trade-off.

Generally, large adult fish can go longer between meals than smaller ones. In fact, big adult fish with slow metabolisms should only be fed once a day.

Goldfish are one of the easiest fish to overfeed. They are large fish with a slow metabolism but are notoriously greedy and eat constantly. Goldfish are also coldwater fish, further exacerbating the problem of overfeeding.

Add the Fancy goldfish’s round shape, and overfeeding your pet fish causes digestive and swim bladder issues, too. For those reasons, it’s a good idea to fast the fish for at least one day per week.

So, How Long Can Fish Go Without Food?

How Long Can Fish Go Without Food

Regardless of their size, most adult fish can go three days to a week without eating before health problems arise.

As previously mentioned, it’s actually good for your fish to fast for a day once a week. Fasting encourages the fish to burn excess fat reserves and helps to clear their digestion.

So, if you need to be away for a couple of days, your adult fish will be fine. However, juveniles and fry need to be fed, or problems will arise.

How To Keep Your Fish Fed During a Vacation

If you plan on a vacation of more than a few days, you’ll need to make plans for your fish to be fed while you’re away. Here are a few practical ways to ensure that your fish don’t go hungry in your absence.

Automatic Fish Feeder

We recommend an automatic fish feeder as the best solution for feeding your fish while you’re away.

An auto fish feeder stores prepared dry foods in a hopper. You program the feeder to dispense a portion of food as often as you wish. Note that some feeders can only dispense dry foods, such as flakes or pellets, which is no good if you have fish that need a diet of frozen or live foods.

Fish Sitting Services

If an automatic fish feeder is not suitable for your fish, you might want to use a fish-sitting service.

Fish sitters can feed your fish so that they eat properly. A sitter can also remove a dead fish, so the deceased doesn’t rot and pollute your water.

If you’re away for a week or more, a pet sitter can carry out a partial water change, tidy up living plants, and test the water to ensure it’s safe for your fish. A good sitter can even dispense medicines if you have a sick fish.

A competent fish sitter might even call you with updates on how your fish are doing or send photos of your aquarium.

If you can’t find a professional, experienced fish sitter to do the job, you might want to ask a friend or relative. However, it’s best if the sitter knows something about keeping fish so that they don’t overfeed your fish or miss something crucial that could affect the health of your whole setup.

Fish Food Blocks

Fish blocks can be a simple option for feeding your fish while you’re away.

You can buy feeding blocks of different sizes to keep your fish fed no matter how long you’re away. All you do is put the block into the tank and allow it to dissolve and release the food gradually.

Food blocks are mineralized blocks or pyramids of animal and vegetable protein. These vacation feeders slowly release the nutrients into the water, providing constant feeding. The main issue with these automatic feeders is that they constantly dissolve.

So, even after your fish have stopped eating, the dissolution process continues, potentially leaving a lot of uneaten food rotting in your tank. One solution used by many manufacturers is to lower the nutritional content in the blocks. Although that approach makes sense, you’re providing poor-quality food for your fish. 

One Solution Doesn’t Fit All!

Unfortunately, many fish species don’t recognize food blocks as food. For example, tetras and most cichlids are not grazing fish and often don’t realize that the block is a food source.

Final Thoughts

If you need to go away for a few days, leaving your fish without food, don’t panic!

Most fish species benefit from a day or two each week when they aren’t fed. That fasting time allows the fish to burn body fat and clear their digestion, helping to prevent constipation, bloating, and its associated swim bladder problems.

What arrangements do you make for your fish if you’re away on vacation? Tell us in the comments section below.

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