The short answer
Chewy, a pet retailer, says a healthy adult fish in ideal conditions can generally go three to five days without food (its FAQ says usually three to seven), and that 10 to 14 days, possible for some fish, is not recommended. An aquatic vet it quotes cautions against fasting juveniles for more than 12 to 24 hours.
Every other figure depends on the fish, its age, its health and the water temperature, and the sources below do not all agree. The chart gives each source’s number with the fish it covers. The sections after it show where your own fish fit, and pond fish come last because cold water changes the answer.
Planning a trip? Our guide to feeding fish while you’re on vacation covers sitters, automatic feeders and feeder blocks. This page sticks to how long fish can go unfed.
How Many Days Can Fish Go Without Food? The Chart
Each row is one source’s own figure, with the fish and conditions it names. None is a guarantee, and where two rows cover the same fish, the sources differ.
| Time without food | Fish it covers | Source (type) |
|---|---|---|
| No more than 12-24 hours | Juvenile fish (Dr. Veronica Pardini, aquatic vet) | Chewy (retailer) |
| Feed every day or two | Herbivores, small active fish, baby fish | Aqueon (maker) |
| A weekend (no day count given) | Virtually all fish except newly hatched fry | Aqueon (maker) |
| Just a few days; a long weekend “might be a stretch” | Tiny species such as Boraras; stomachless fish such as pipefish | Practical Fishkeeping (magazine) |
| Generally 3 to 5 days | Healthy adults on a proper diet in ideal conditions (Chewy’s article) | Chewy (retailer) |
| Usually 3 to 7 days | Healthy adults in ideal conditions (Chewy’s FAQ) | Chewy (retailer) |
| About 5 days | A community of plump, healthy fish | Practical Fishkeeping (magazine) |
| Often one week | Adult fish, depending on size, metabolism and water temperature | Aquarium Co-Op (retailer) |
| A full week, two at most | Most adult fish (Dr. Benjamin Rosenbloom, vet); Chewy rates skipping meals “Inexpensive, but risky” and best for “those traveling for a week or less” | Chewy (retailer) |
| 10 to 14 days, not recommended | Some fish | Chewy (retailer) |
| Often a week or two between meals | Large, infrequent eaters such as shovelnose catfish | Practical Fishkeeping (magazine) |
| One week with no supplemental feeding | Healthy koi in an established pond | Aquascape (pond maker) |
| Several weeks to a few months | Koi and goldfish in a pond in winter, unfed once the water is below 50°F (10°C) | Aquascape (pond maker) |
Most tanks hold more than one kind of fish, so more than one row can apply. Practical Fishkeeping, a fishkeeping magazine, builds its sitter advice around the fish that can’t wait: a visit every few days “unless you have fish that can’t go without eating for 24 hours.” Our reading of the chart, not a source’s rule: plan around the shortest row that fits any fish you keep. Chewy adds: “Always check with your veterinarian for how long is appropriate for your individual fish.”
Where Your Fish Fit: What Sets the Limit
Chewy says how long a fish can go without eating “depends on factors such as species, size, age, and condition.” Chewy’s vacation page names “The age, water temperature and species of fish” as the most important factors. Check each one for your own fish.
Water temperature
Dr. Robert Martinez, a certified aquatic veterinarian quoted by Chewy, explains that a fish’s metabolism is influenced by the surrounding water temperature. Chewy adds that tropical fish in warmer water have faster metabolisms than coldwater fish and “need to eat more often to maintain optimal health.” Chewy’s example: freshwater angelfish, kept at 70-80°F, may need feeding more often than goldfish, which prefer 50-60°F.
Aqueon, a fish-food and aquarium maker, agrees: “Water temperature regulates fishes’ metabolisms and influences how often and how much they need to be fed.” It says small active fish such as danios and newly hatched fry should be fed frequently, “especially when kept at warmer temperatures.”
Size and activity
Chewy says small fish have faster metabolisms than larger fish. Its example is the tiger barb, a very active swimmer of two to three inches, which during a fast is likely to burn through its energy stores more quickly than a larger, more sedate species such as the gold severum. Aqueon puts it this way: “Large fish, especially carnivores or older fish, don’t need to eat as frequently since they have larger fat reserves than herbivores and smaller fish.”
Diet: grazers, stomachless fish and predators
Chewy reports that grazing herbivores and omnivores, such as blennies and goldfish, “may require smaller, more frequent feedings than predatory fish that may go weeks between meals in the wild.” It adds that carnivores such as bettas and oscars may be able to go longer without food than sizable herbivores such as plecos.
Fish without a true stomach are a separate case. A Southern Regional Aquaculture Center fact sheet by University of Florida researchers says: “Goldfish and common carp lack true stomachs, so they benefit from multiple feedings each day.” Dr. Rosenbloom, quoted by Chewy, says stomachless grazers “such as goldfish and suckermouth catfish, would likely need more regular feedings.”
At the other end, Practical Fishkeeping says of large, infrequent eaters like a shovelnose catfish: “Such fish will often go a week or two between meals.” Aquarium Co-Op, an aquarium retailer, says large predatory fish “may only need to eat a few times a week.”
Age: fry and juveniles
By the sources above, young fish can wait the least. Dr. Veronica Pardini, a certified aquatic veterinarian quoted by Chewy, cautions against fasting juvenile fish for more than 12 to 24 hours while they are still developing, and Chewy says juveniles “need to be fed regularly to prevent stunted growth.”
On its vacation page, Chewy reports Dr. Rosenbloom says newly hatched fish “may need to be fed 3-8 times per day with a high protein diet.” Aquarium Co-Op says growing babies and slow grazers “often need access to constant food” and may need three to five tiny meals a day. Aqueon’s weekend figure leaves out newly hatched fry.
Health and condition
Most of the figures above are for healthy fish. Chewy says fish that are stressed, sick, thin or malnourished need regular feedings, and its FAQ is plain: “Fasting is never recommended for juveniles and fish recovering from illness, injury, or malnutrition. Never let your fish fast without first speaking with your veterinarian.” Practical Fishkeeping’s five-day figure excludes undernourished fish.
Note
In a tank at its usual temperature, a fish that stops eating by itself is a different problem from a planned fast. Test the water for ammonia and nitrite (see our guides to lowering ammonia and lowering nitrite) and contact an aquatic veterinarian. Pond fish are different: Aquascape says koi and goldfish become less active and need less food as pond water cools (see the pond section).
Reef fish
For saltwater keepers, Dr. Pardini says withholding food may be unsafe for fish with high metabolic rates, such as certain reef fish, which “can rapidly lose body condition without consistent feeding and may pass the point of recovery sooner than other species,” as Chewy reports it.
Goldfish and Bettas
Chewy’s FAQ gives figures for two popular fish, each with a warning:
- Goldfish: “A healthy goldfish may be able to go seven to 10 days without eating, but this is never recommended.” Chewy adds that “Feeding gaps of more than five days will likely start to impact their health,” and that higher water temperatures reduce a goldfish’s ability to go without food.
- Bettas: “A healthy adult betta fish can survive up to 14 days without eating, but this is never recommended,” Chewy says, because it “may lead to stress and other health issues.”
For goldfish in an outdoor pond, Aquascape’s winter figure below covers koi and goldfish; its one-week figure covers koi only.
Do Fish Need Feeding Every Day?
Sources differ on feeding frequency:
- Chewy: “Yes, feed your fish every day to ensure proper nutrition and maintain a healthy metabolism,” offering only as much as the fish eat within two to three minutes.
- Aqueon: “For the most part, feeding your fish once or twice a day is sufficient. Some hobbyists even fast their fish one or two days a week to allow them to clear their digestive systems.”
- Aquarium Co-Op: “Most fish are fine with being fed once a day,” and, as a fix for overfeeding, it suggests keepers “consider introducing a weekly fasting day.”
Dr. Pardini, as Chewy reports her, says “healthy adult fish can benefit from occasionally skipping meals” and that overfeeding is a bigger danger than underfeeding. Aqueon makes a similar point: “It’s always best to underfeed, especially in new aquariums, as uneaten food can cloud your water and cause dangerous rises in ammonia and nitrite levels.” Before any fasting day, Chewy’s FAQ applies: “Never let your fish fast without first speaking with your veterinarian.” It rules out fasting for juveniles and for fish recovering from illness, injury or malnutrition.
For pond fish, Texas A&M AgriLife Extension says fish are cold blooded, “so they do not have to be fed each day.”
When Your Fish Can’t Wait That Long
For a tankful of newborn fry that need constant feedings, Aquarium Co-Op says “it may be best to set up an automatic fish food feeder or find a pet sitter.” For a healthy community, Practical Fishkeeping says that past about five days you need a contingency feeding plan. Our vacation feeding guide compares sitters, automatic feeders and feeder blocks, with the cautions makers and vets give for each.
Practical Fishkeeping and Aquascape agree on one point: don’t feed extra before a fast. Practical Fishkeeping warns, “Extra food going in means extra waste coming out, and doing so will only increase the pollution risk.” Aquascape gives pond keepers the same advice: “Feed normally before your trip. Do not give extra food.”
Ready to buy?
For the days you do feed a tropical tank, our tropical fish food roundup compares each food form, from flakes and granules to pellets and crisps.
Pond Fish: Water Temperature Sets the Clock
Koi and pond goldfish live by different numbers outdoors, because the pond feeds them too and cold water slows them down. Texas A&M AgriLife Extension, a university extension service, reminds pond keepers that their fish are “in an outdoor environment and you are providing only supplemental feeds,” since they also eat algae, zooplankton, insect larvae and some plants. It adds that “feeding must be reduced or even ceased during cooler winter months when their metabolism is not active.”
Aquascape, a maker of pond products, says “Healthy koi in an established pond generally do not need supplemental feeding if you are away for one week,” and “It is generally safer to skip feeding than to have someone accidentally overfeed the fish.” It also says: “Koi and goldfish can typically go several weeks to a few months without eating during winter.”
Aquascape (pond-product maker), feeding by pond water temperature:
| Pond water | Aquascape says |
|---|---|
| Above 60°F (15.6°C) | Keep feeding an appropriate food, by activity and appetite |
| 50-60°F (10-15.6°C) | Switch to a cold-water food; feed less, and less often, as it cools |
| About 50°F (10°C) or below | Stop feeding; resume only when the water stays above 50°F and fish seek food |
Oklahoma State University Extension (university), feeding rates by water temperature:
| Water | Oklahoma State says |
|---|---|
| 45-59°F | Growth rations (not maintenance): 0.5% of body weight a day at 45-49°F, 1% at 50-59°F. Maintenance rations, fed 5 days a week: 0-0.2% at 45-49°F and 0.2-0.5% at 50-59°F, the higher figure for fish over 1/2 pound |
| Below 45°F | Fish do not feed |
To place your pond in a table, Aquascape says to “use the pond water temperature, not the outside air temperature,” checked with a pond thermometer, and warns that “A brief warm day does not necessarily mean pond water has warmed enough for feeding.” Sources differ on the stop point: about 50°F for Aquascape, 45°F for Oklahoma State, and no single temperature in Texas A&M’s manual. Texas A&M adds that fish should be fed sparingly in temperatures above 85°F, since warmer temperatures and high feeding rates can lead to oxygen depletions.
For trips, the two sources differ. Texas A&M suggests that if you will be away “for a few days or more,” a “pond babysitter” regularly checks the pond for problems and feeds the fish and plants. Aquascape says skipping feeding is generally safer than a sitter who accidentally overfeeds, and that if someone will feed the koi, “pre-measure each feeding.”
Frequently Asked Questions
Q. Can fish go a day or two without food?
A day or two is shorter than either of Chewy’s ranges for healthy adults in ideal conditions (generally three to five days in its article, usually three to seven in its FAQ). That is our reading, not a figure Chewy gives. Juveniles are the exception: the vet Chewy quotes cautions against fasting them for more than 12 to 24 hours.
Q. What happens if you don’t feed your fish for 3 days?
Chewy says a healthy adult on a proper diet in ideal conditions can generally go three to five days without food “without experiencing lasting consequences,” and its FAQ says such fish can usually fast three to seven days “without serious risk to their health.” The risk rises for fry and juveniles, small active fish, reef fish with high metabolic rates, and fish that are sick or thin.
Q. Can fish go 4 or 5 days without food?
Four or five days sits inside Chewy’s ranges for healthy adults in ideal conditions (three to five days in its article, three to seven in its FAQ). For goldfish, Chewy says gaps of more than five days will likely start to affect their health; for healthy koi in an established pond, Aquascape gives one week.
Q. Can fish live on what grows in the tank?
Chewy says some fish feed on the algae and microfauna a healthy tank grows, but “it’s generally just a snack and not a primary food source.” Pond fish are different: Texas A&M counts algae, zooplankton and insect larvae as part of what they eat.
Q. What do fishkeepers on forums report?
In a FishLore forum thread about an eight-day trip, one member wrote “I leave 10 days regularly and the fish are fine,” and advised feeding as normal rather than extra before leaving. That describes one keeper’s tanks, not a tested limit; Chewy says fasting for 10 to 14 days is not recommended.
Sources (13)
- Chewy, How Long Can Fish Go Without Food? 5 Ways to Keep Your Underwater Friend Safe on Vacation (retailer; quotes aquatic veterinarians)
- Chewy, How to Feed Fish While On Vacation: 5 Options (retailer; quotes a veterinarian)
- Aqueon, Traveling? Here’s How to Prep Your Aquarium Before You Go (maker)
- Aqueon, How to Properly Feed Your Fish (maker)
- Aquarium Co-Op, How Often to Feed Fish (retailer blog)
- Practical Fishkeeping, How do I look after my aquarium while on holiday? (magazine)
- Southern Regional Aquaculture Center, Species Profile: Koi and Goldfish (SRAC 7201) (university fact sheet)
- Texas A&M AgriLife Extension, Ornamental Fish Ponds and Water Gardens (university extension)
- Oklahoma State University Extension, Water Gardens (university extension)
- Aquascape, Should I feed my pond fish during the winter? (maker)
- Aquascape, When should I stop feeding pond fish in the fall? (maker)
- Aquascape, Do I need to feed my koi while I’m on vacation for a week? (maker)
- FishLore, How long can fish be left without food? (forum)
