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How Long Can Aquarium Fish Go without Eating?

How Long Can Fish Survive without Food in an Aquarium San Diego, CA

All aquarium species need frequent nourishment to live healthy lives, but some happen to be more resilient than others, particularly those kept in freshwater tanks. Let’s say you have a healthy 10-gallon tank with a few guppies, danios, and goldfish plus a few plants along with shrimp. In this case, cutting off feeding for two days won’t have much of an effect. The species will realize something has happened to their regular nourishment, and they’ll start feeding on algae, shrimp, and microorganisms. Once algae and microshrimp are all consumed, the fish will eventually turn on each other for survival. Of course, the most humane thing to do is supply the fish with food via an automatic feeder. Here are a few things to consider when it comes to how long fish can survive without food in an aquarium.

Established Aquariums Versus Newer Tanks

The scenario above requires a highly nourishing ecosystem, and it’s almost like a lost ship where crew members only have barrels upon barrels of hearty stout beer to consume. It’s not adequate nutrition and could result in adverse health conditions. You generally shouldn’t stop feeding your fish for more than two days, and this should never be attempted in a tank that has been recently established without plants or shrimp.

Going on Vacation

If you’re only going to be away for two days and your tank has already been established, you should have other considerations in mind. Test the water and make sure the ammonia levels are lower than 1 ppm. Anything higher would need a 50 percent replacement of water treated with conditioner and beneficial bacteria. After changing the water, don’t forget to test it once again before leaving, and you can double the feeding at this time, spreading the feeding out over a few hours. It’s generally a good idea to assign the feeding task to a friend, roommate, or relative. To take this a bit further, add the exact amount of food you normally feed to a Ziploc bag and mark it for the day to be used (as in Monday the 10th). This way your friend doesn’t end up “loving your tank to death” with the old “well, they looked hungry” statement.

Automated Feeders

These devices are the most ideal replacements for human fish sitters who take care of the feeding when you’re away for more than two days. Why? Because they don’t forget and they get the job done correctly and are battery powered, like the ones we have at Aquatic Warehouse:


The worst are the vacation feeder blocks that are dropped into the tank. Mechanical feeders that can be programmed to drop measured amounts of flakes and pellets, which you can acquire from a reputable aquarium supplier like Aquatic Warehouse, are better in this regard.

Live Food Options

Brine shrimp, infusoria, and “water fleas,” which are actually plankton, offer greater nourishment to aquarium species in terms of proteins and vitamins. If you feed these organisms to your aquarium fish prior to going on vacation, their resilience will increase while you’re away, and this will complement a feeder block in case it runs out ahead of time. When plankton blooms in the aquarium, your fish will have greater nutrition for a few more days.

Every species of fish is different, so make sure to find out your tank inhabitants’ dietary needs before changing anything about their feeding schedule. If you have any questions about how to keep your fish healthy and happy, contact the aquarium and pond experts and Aquatic Warehouse. From aquarium and pond filters to beneficial bacteria and nutritious fish food, we have everything you need. Stop by our store in Kearny Mesa, or give us a call at 858-467-9297.


Contact Information

  • Address: 5466 Complex Street Suite 204
    San Diego, CA 92123
  • Phone: (858) 467-9297
  • Email: sales@aquaticwarehouse.com
  • Working Days/Hours: Mon - Fri / 10:00 AM - 7:00 PM
    Saturday / 10:00 AM - 6:00 PM
    Sunday / 11:00 AM - 6:00 PM


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