How Long Can Fish Go Without Food?

Feeding our fish is a daily activity that’s one of the most enjoyable parts of the hobby! But sometimes our regular schedule gets interrupted and we can’t be there to keep our pets full.

If there’s nothing we can do and we have to be gone for a spell, just how long can fish go without food?


How Long can Fish Go Without Food?

Most healthy aquarium fish can go three days to a week without eating. However, it usually isn’t recommended to go more a day or two without feeding unless completely necessary.

This number may vary based on a few factors:

How Active Are Your Fish?

How long your fish can go without food depends heavily on the metabolism of your fish. Smaller fish tend to be very active, which means they need more food than slower, larger fish.

Small, schooling predators like Tetras and Rasboras tend to be continually active. The way they dart about, nipping at one another and exploring their home is part of their charm!

In nature, these fish would be constantly “grazing” as plankton, insect larvae, and other food sporadically drifts by. In aquariums they get a large feeding all at once, which fills them up for a few hours. Still, you’ll need to provide food 2 or even 3 times per day for these guys!

The warmer the environment, the faster the metabolism of your fish. Many tropicals, like Danios and White Cloud Minnows, can also thrive in room temperature or cooler water.

In cooler tanks, we should be giving them either less food per feeding or offering food less often (1-2 times per day). Any more and you’ll run into either fat fish or uneaten food going to waste.

Are your fish herbivores or carnivores? Since plants tend to be abundant but low in nutrition, herbivores tend to graze continually. They need large amounts of this lower energy food to maintain their weight. Carnivores, on the other hand, can eat a single meal and digest for a longer period without eating.

How Large Are Your Fish?

Body mass is just as important as metabolism and for many fish the two are closely related. Generally speaking, larger fish have slower metabolisms than smaller ones. However, larger fish also need more food to maintain their body weight than smaller ones, so it’s a trade-off.

As a rough rule of thumb, larger (adult) fish can go longer between meals than smaller ones. In fact, adult fish with slower metabolisms like Goldfish really only should be fed a single time per day.

Adult Goldfish are some of the easiest fish to overfeed as they will eat constantly regardless of how much they were fed earlier. Not only does their metabolism slow down as they age but they are also cold water fish.

While you shouldn’t try to test this, most fish can go anywhere from three days to a week without eating before problems arise. In fact, it’s healthy to skip a day here and there, to clear their digestion and encourage them to burn fat reserves. For small fish with faster metabolisms, you can offer a single light feeding every so often for the same results.

If you need to leave suddenly for a two-day weekend, your fish will be absolutely fine. Unless they are small fry, which need constant feeding. But what about if you need to be away for more than a few days? It’s certainly stressful for fish to have their feedings interrupted for a long period of time.


How Can I Keep My Fish Fed During a Holiday?

If you have a longer vacation planned, you’ll need to make sure your fish are cared for in the meantime. Here are some of the most common ways to ensure your fish don’t need to go without food!

Automatic Fish Feeders

Automatic fish feeders are my tool of choice for this situation. These devices store prepared foods in a hopper and can be programmed to dispense some as often or as little as you wish.

I highly recommend having an automatic feeder on hand a few days before your trip so you can work the system out and ensure it operates properly. Some are only capable of dispensing a single type of prepared food (i.e. only flakes or pellets) so choose carefully.

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The Torlam is a more versatile model that comes with additional options for flexible operation. It can be calibrated to give double or triple feedings at certain times of the day. For example, you can program one to drop a small, single serving of pellets at night for your plecos but give a triple feeding at noon for the community.

And once you return home, you can keep the unit installed but use the manual override button to have the pleasure of personally feeding your fish. But should business take you away, the Torlam Auto Feeder will dispense food as normal.

Fish Sitters

Having a neighbor, relative, or friend drop by to feed your fish is another common way to make sure your fish eat properly.

Fish sitters can also do things automatic feeders can’t, like remove a fish that’s died during your vacation so it doesn’t rot and cause further problems. Or call you to provide updates, send photos of the tank, and more.

I feel best if my fish sitter knows something about aquariums so it’s good to be a part of a local aquarium club or have a partner that knows fish! People who aren’t familiar with fish may underfeed or much worse, overfeed.

A competent fish sitter can also perform tests on the pH, ammonia levels, or even dispense medicines for a sick fish.

There are few worse things to return to after a long holiday than green aquarium water, foul smells, fungus-covered food, or ich. So choose your fish sitter carefully!

Food Blocks

While they look strange food blocks have been around for decades and are an inexpensive, incredibly easy way to keep your fish happy. They can last weeks and don’t need calibration or directions on how to operate!

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As vacation feeders go, these products are okay. They are certainly the simplest way to keep your fish fed over your trip. However, I don’t use these myself and I would caution you if you decide to buy one for a few reasons.

Food blocks are essentially mineralized blocks of vegetable and animal protein. The mineral powder slows the release of nutrients into the water. While this is a smart idea, the problem is that the release is constant.

Once your fish stop eating the dissolution process continues. Manufacturers try to balance this by lowering the nutritional content, which makes sense. Except now we’re just providing low-quality food to our fish. Better than nothing but far from ideal.

Also, many fish won’t even recognize these blocks as food. Many community fish, like Guppies and Barbs, are pretty versatile and willing to pick at anything.

But I would worry using one of these with fish accustomed to a big mouthful of food, like Cichlids. Tetras aren’t grazers either and might not recognize a food block. So consider your fish, their nutritional needs, and your vacation time carefully to decide whether this product is right for you.


Conclusion

We’ve learned that fish can go anywhere from three days to a week without eating before they start to suffer. And that the exact range depends on the temperature, their size, metabolism, and diet.

Instead of testing this, it’s best to use one of the three methods detailed above to keep your fish fed if you have a trip longer than 2-3 days coming up. So safe travels and may your fish be well fed in the meantime!

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