How Long Can Fish Live Without Food?

Ah, the sixty-four million dollar question, how long can aquarium fish live without food? Can you leave them for a couple of weeks whilst you go on vacation? Can you leave them for a long weekend? Or do they need food every single day to keep them in the best of health?

Let’s find out!

Food, Glorious Food!

Fish love food, and like many other creatures, they will take every opportunity to eat it that they are given. Big meals, small meals, treats, aquatic plants, and even other fish in the aquarium, they will feast upon it all. They get excited at the sight of food, fight for food, and may even beg for it, food has to be one of the most important things in their life.

The truth is, however, that what may seem like greed, even bordering on obsession, is really only the instinct to survive. Feeding heartily, when they get the chance, is an inherent trait that stems from life in their natural world.

Read our complete Guide to fish food here!

Take the Angelfish, for example, an omnivore that feeds on insects and crustaceans, in the main. They don’t always have a constant supply of foodstuff to hand in their natural environment and have to take the opportunities to feed when they can.

In the home aquarium, this feeding frenzy behavior has led to the belief that fish NEED a lot of food, and that they NEED it on a daily basis. This, however, isn’t strictly true but has led to many aquarists overfeeding and panicking over missing even one day’s feed.

discus fish feeding

So How Long Can A Fish Go Without Food?

Asking how long a fish can survive without food is a little bit like trying to guess the length of a piece of string. The answer will vary depending on the specific fish or piece of string in question, a ‘one size’ answer doesn’t fit all!

Generally speaking, most tropical fish have a surprising ability to fast and survive. Almost all species can go at least a few days without being fed anything, with some like Cichlids going up to ten days. Older fish that are larger will do better without food than smaller and younger ones. Herbivores that eat daily, will suffer more than carnivores that tend to eat only every few days. Fish Fry are the most at risk when left unfed, fish this young will only last a day or two.

How Will I Know How Long My Fish Can Go Without Food?

Truthfully, there is no real way of knowing unless you test them by not feeding and monitoring how they do. This, however, is not something we would recommend as it could be detrimental to your fish’s health, even causing death. Rather, we would suggest that you only, if necessary, leave your fish without food for three to four days and that you take a few steps to decrease their appetites.

The first trick you can use to slow your fish’s appetite down is to lower the temperature of the aquarium slightly. The second is to lessen the length of time that you have your aquarium lights on. Taking these steps will decrease the activity that your fish participate in, slow down their metabolism, and decrease their need for food.

fish feeding

I’m Going Away For A Week Or Two, How Will I Feed My Fish?

There are three ways you can feed your fish during long periods away from home. The first is to ask a friend, relative, or even a fish sitter to pop in and look after your fishy babies in your absence. Be sure, however, if you take this route to ensure your ‘sitter’ knows what to feed, how much to feed, and all about any maintenance they will need to perform.

Your second option is to purchase a vacation feeder which usually comes in the form of a block that slowly releases pieces of food over a week or two. These, however, are not ideal as they often do not contain the correct nutrients your fish needs, nor are they what your fish are used to eating. Due to this, your fish may choose not to eat it leaving you with a very messy aquarium and poor water quality on your return.

The third and final option is to invest in an automatic feeder. These are usually battery or electric-powered and can be set to release items such as flake, pellet, or dried food on a regular basis. Most can feed your fish for up to a two week period. They have the benefit of allowing you to feed your fish their normal diet.

Conclusion: How Long Can Aquarium Fish Live Without Food?

Whilst we have been unable to answer the original question exactly, we hope that you are now a little clearer on how long it is feasible to leave your fish without food. Three to four days is the maximum we would recommend, and then you need to be looking at alternative options.