Fish Swallows Fish Whole – Can You Still Save Your Pet?

Keeping only a fish in a single-species aquarium is one thing. But keeping more than one fish in an aquarium is another thing entirely. If you pair the wrong fish sizes, some will swallow and eat other fish.

Sometimes, this is accidental, and on many others, it is intentional, especially when you starve a predatory fish species. The question on the mind of many concerned enthusiasts is what happens when a fish swallows another fish whole. And whether you can still save the smaller fish?

This piece discusses the answer to that question, whether you can still save your pet, and other vital concerns.

Read on to find out.

Can Fish Swallow Fish Whole?

Yes, fish can swallow fish whole. Many factors cause this behavior, but the main reason fish can and will swallow fish is the difference in size.

For instance, large freshwater fish species like the Jack Dempsey that grow to a maximum length of about 6 inches are likely to swallow small fish like the Gulf Coast Pigmy sunfish if housed in the same aquarium.

Many other factors that can make a fish swallow other fish whole include the following:

Wrong Diet

Carnivorous fish species need high protein feed as opposed to plant-based feed options. Carnivorous fish species need about 70% protein.

Failing to provide your fish with the proper nutrition could lead to starvation. Upon starvation, it is hardly unlikely that your carnivorous pets will not look at the smaller fish as food.

Improper Introduction Tactics

Introducing fish right is a great way to prevent one from swallowing the other. When introducing Bettas to a tank of nerite snails, you are often advised to bring the Betta into the tank in a breeding box to become accustomed to the Nerite snails.

It is also recommended that you introduce the Betta fish last. This way, it will regard the snails as part of the ecosystem.

The same logic applies here. For many species, it would be best to introduce the predator last. If you introduce the predator first, introducing any other smaller fish will be perceived as an invasion of privacy, and your pet may be swallowed at the slightest confrontation.

But when you introduce the predator last, there is a great chance it will regard all the tank mates in the tank as part of the decoration and will have no right of territory nor one to defend from invaders.

Wrong Tankmates

Pairing small fish species like tetras or other 1-3 inches with a large carnivore like the Afer knife fish is a classic example of choosing the wrong tank mates. That would be a grave mistake as the Afer knife can swallow your smaller fish accidentally or intentionally.

It is therefore of utmost importance to understand the size distribution of the species in your community tank and how you can pair close sizes together. Predatory fish of similar sizes usually respect themselves more often than if paired with a smaller fish.


Invasion of the territory is a possible cause for one fish swallowing another. Many fish species are territorial and will not hesitate to defend their territory if needed.

One great way to tackle this is to use an appropriately sized community aquarium with enough decorations. This will reduce the chances of a confrontation between the tankmates. When the chances of a confrontation are limited, the chances of your larger pet swallowing your smaller pet are greatly reduced.

Cannibalistic Tendencies

Many fish species feed on their younger ones after they hatch. This is especially the case with a community tank with juveniles housed in the same tank with a fish that is big enough to swallow them.

Also, many fish species have strange parenting patterns. Clownfish, for instance, eat newly hatched babies and will also swallow juveniles that are small enough to be swallowed. Many other fish species also share the same traits.

What Happens When Fish Swallows Fish Whole?

The worst happens when your large Flowerhorn Cichlid swallows your Indonesian Super Dwarf fish. At best, the swallowed fish will be alive for no more than 15 minutes from when it is swallowed. The main cause of this rapid death would be the lack of oxygen.

The temperature of the water when the fish is swallowed also determines how fast the digestion process will take. The digestion will be slower at a lower temperature range than when the fish is swallowed in a warmer water temperature.

The process of digestion usually starts as soon as the fish is swallowed. So, if your bigger fish in the aquarium accidentally swallows a smaller fish, there is a high chance that the smaller fish is already dead or will be in the next 15 minutes.

Can You Still Save Your Pet?

The chances are very slim. If you want to save your pet, the best you can do is to put up preventive measures to ensure that your fish is not swallowed.

As mentioned above, the digestion process is a very fast one. At best, your pet would have died within the first 25 minutes in the stomach of the bigger fish.

Even if it were possible to have the fish vomit your pet back within less than 15 minutes, there is a great chance that your fish will still die. The worst part is that it would most likely die a more painful death.

This is because the absence of oxygen would have caused severe damage to its brain, which damage would eventually lead to death. Apart from that, it is very unlikely that your pet will still have its sight.

The stomach acid would have damaged its eyes before its regurgitation. So, in the end, it will eventually die. But it will die a slower and more painful death.

If there is anything you can do to save your pet, it would be to set up preventive measures to ensure that the chances of your pet getting swallowed are extremely reduced.

How Can I Save My Pet?

Frankly speaking, there is hardly anything you can do once a bigger tank mate has swallowed your small fish.

As explained above, the fish will have died from the lack of oxygen within the first few minutes. Even if it is regurgitated, it is most likely to be blind and will inevitably die in a short time. So the best way to save your pet is to ensure that the chances of it being swallowed are as low as possible.

Of course, choosing the right tank mates is the first step to saving your pet. If you keep a community tank with many small-sized fish, especially feeder fish species like younger tilapias, guppies, platies, and even cichlid fries, it would be best to choose tank mates in the same size category.

At most, you want to stick with tankmates that are not big enough to swallow these smaller fish.

Another way to handle this problem is to understand your pet’s profile. If you have a large predatory bottom dweller, it would be a bad decision to pair it with smaller bottom dwellers. Instead, it would be best to pair it with a bottom dweller that is equally large and aggressive enough to be respected.

Finally, you can prevent your pet from getting swallowed by ensuring that the dietary needs of your fish are met. This means getting the right food, feeding the right amount, and ensuring that your feeding frequency is right.

If you keep carnivores, it would be best to feed them crude protein instead of plant-based flakes and pellets.

Other things you can do to save your pet include the following:

Make Arrangements for Enough territories in the Tank

You can reduce the chances of your fish getting swallowed by ensuring enough decorations, caves, and other aquascaping to help all the different species find their place in the ecosystem.

Without tank decor, all the occupants in your tank will see each other more often and bump into each other more often. This only increases the chances of your pet getting swallowed.

But with rocks and caves to hide in, and plants that set boundaries, your vulnerable pets can hide when they feel threatened. Also, the chances of accidental swallowing are significantly reduced.

Monitor the Activities in Your Community Tank Closely

Monitoring the activities of each fish in your tank is critical for preventing a fish from swallowing another. If you have spawning fish and do not wish for any juvenile to be swallowed, monitoring the activity in your tank will help you know when to separate the fries or juveniles from the others.

Also, Monitoring helps you know the culprit if your smaller fish begin to disappear from the tank. Monitoring will help you identify the culprit in time to expel it from the ecosystem before it swallows all your precious smaller fish.

Bottom Line

It is not uncommon for fish to swallow other fish entirely in the aquarium. While there is a lot you can do to avoid this ugly situation, there isn’t much you can do after the worst has happened.

So, the best way to save your pet is to implement these preventive measures to limit the chances of your vulnerable fish becoming fish food for larger tank mates.