How Long Can Fish Go Without Food

Fish comprise a widely diverse class of aquatic vertebrates. Ranging in size from the enormous whale shark to the tiny neon tetra, fish exhibit varying behaviors regarding feeding and food sources. These variances include differences in their ability to go without food for prolonged periods of time.

Categories Of Fish

Fish fall into one of four categories based on diet. These are carnivores, herbivores, omnivores and limnivores. Carnivores such as sharks and cichlids eat meat. Tangs are herbivores and consume plants and algae. Limnivores eat mud-based foods and omnivores eat both plants and other animals. These distinctions have an impact on feeding frequency.

In general, carnivorous fish can survive longer without feeding than other fish. In nature, carnivores often go days without catching prey and are designed to withstand periods of food scarcity. The other categories require more frequent feeding to survive. Herbivores and limnivores spend the majority of time eating and searching for food. This is due to the fact that the plant matter consumed has a lower nutritional value.

Extremes In Feeding Behavior

Salmon spend most of their lives in salt water. During their time in the ocean they eat constantly, building up fat stores that will enable them to spawn in fresh water. Moving from salt to fresh water shocks the salmon’s internal organs, shutting down their digestive systems. They can survive for months on the stored fat but will eventually die after spawning.

Sharks need to consume between 0.5 to 3 percent of their body weight daily to maintain their health. Slow metabolism enables this requirement to be accomplished with a large catch that can allow the shark to go up to two weeks between feedings.

The plecostomus is a limnivore and eats mud-based foods. They constantly feed on algae and other microorganisms, slowly grazing along the bottom of an aquarium. Its appetite and food choice make it an excellent aquarium tenant as it helps keep the tank clean as it feasts.

Common Aquarium Fish

Discus and cichlids larger than 10 cm can survive up to two weeks without feeding. This is true of most fish this size. Some larger fish can survive for several months.

Guppies, tetras and other smaller fish will not make it as long. They should not go more than a week without food.

Goldfish will be able to withstand up to two weeks without feeding.

Factors That Affect Feeding Requirements

There are some steps that can be taken to slow the metabolism of tropical fish and limit both their desire and the time available to search for food. Lowering the temperature a few degrees will slow the metabolic processes of the fish and lessen the demand for food.

Reducing the amount of light an aquarium receives will also help in lowering the food demands of its inhabitants. A timer set to allow 6 hours of light rather than that of a full 12 hour day will both slow down food consumption and allow the resting fish to burn less calories thereby limiting their hunger.

The age and size of the fish and the aquarium itself are also important factors regarding the ability of the fish to survive without being fed. Older fish have stored fat in their body mass and can survive for longer periods of time than younger fish. Baby fish cannot survive more than day or two without feeding.

A well established aquarium can be left for longer periods of time than a new one. In an ecologically balanced aquarium the tank mates have experience surviving in this environment. Regular water changes and some algae growth will aid the ability of the fish to survive longer. It can be dangerous to leave a new tank for extended periods of time.

Vacation Feeding For Aquarium Fish

If you are planning to leave your fish for an extended period of time there are some steps you can take to minimize the risk to the fish. Perform a partial water change a few days before departing and clean your filter thoroughly. Feed the fish well for at least the week before you leave. As stated above, lower the temperature a few degrees to slow down the metabolism and use a timer to reduce the amount of time the aquarium is lit.

A good sense of how your aquarium and its inhabitants will hold up while left alone is to keep a “hands off”approach for a length of time. Do not feed or maintain the tank and observe how everyone is doing. This should be done some time before you leave and prior to the aforementioned water and filter changes.

During an absence of a few days these steps should suffice to maintain the health of your fish. Use their size and age as a guide for the amount of time you can safely avoid feeding them.

If you will be gone for a longer period of time there are some food delivery options. Automatic feeders are available which can be set up to feed specific foods at timed intervals. Feeding blocks that slowly dissolve and release food pellets are also available but are not as reliable as automatic feeders as they can be adversely impacted by the tank’s PH levels.

How Long Can Your Fish Go Without Food

As you can see there are a number of factors to be considered before leaving your fish unfed for any length of time. Understanding the species that you are keeping is critical to planning their survival. A well maintained aquarium stocked with healthy, well fed fish is the first step. This will enable them to get though their period of fasting with no ill effects. They will be happy to see you on your return.

About the author

Toby Sanders

With more than 15 years of experience in aquarium sector, i'm totally passionate about creating Aquarist Guide blogspot. I enjoy sharing all of my knowledge to help you guys effectively build your own tank. I believe that when you find the easiest way to raise your lovely fish successfully throughout my blog, you will definitely fall in love with fish keeping more than a popular hobby.

Mary - July, 2018

I have an Freshwater Angelfish that has stopped eating. I have offered several varieties of food and even tried a small pea, NOTHING!!!! I reached out to an Angelfish breeder on f/b and she told me to treat his tank with Kanaplex . Reached last dosage, NOTHING!!!! Do you know what else to do?????
Any helpful advise will be greatly appreciated. Thank you in advance.

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