Do Betta Fish Float When They Die?

Do Betta Fish Float When They Die?

I’m sure we have all seen pictures of the stereotypical “belly up” dead fish, but is that an accurate representation? Can fish go belly up but still be alive? How do you know if your fish is dead?

Not all betta fish float once they die. In fact, most of the dead betta fish you may find will be on the ground or in their favorite decoration. Some betta fish may go belly up but still be alive due to a disorder called “swim bladder disorder”, so don’t automatically think your fish is dead even if it is upside down. In the same vein, just because a fish is laying on the bottom and looks dead doesn’t mean it actually is.

In this article, we will cover swim bladder disorder, how to tell if a fish is dead, decomposition, where a dead betta may end up, and ammonia and nitrite spikes.

Swim Bladder Disorder

The swim bladder is an organ that helps a fish control their position in the water. They take air into this organ in order to rise in the water and let air out in order to sink further down. However, this organ can develop disorders, just like any other organ, which will result in either a sinking or floating betta.

If your betta floats, it is called a positive buoyancy disorder. This form of swim bladder disorder is fairly common and may result in people giving up on their fish too soon. Most of the time, the fish will look like it is constantly rising to the surface and may get stuck at the surface for some time.

They may even go belly up, depending on the severity of the disorder, but this does not mean they are dead or dying. Even if your fish goes belly up and gets stuck, it does not necessarily mean that your fish is doomed.

Constipation is the most common cause of swim bladder disorder. To fix this, fast your fish for 3 days, then feed either frozen daphnia or a piece of a blanched, deshelled pea. After you fix the disorder, feed your fish an amount of food the size of its eye twice a day.

The same treatment can be used if your fish is constantly stuck at the bottom of the tank. A negative swim bladder disorder will prevent your fish from swimming to the top properly. It will force your fish to struggle in this even, but most of the time it will still be moving. If your fish is lying on its side at the bottom of the tank, the issue is likely something else.

How to Tell if a Fish is Dead

If you notice your little fish either belly up or stuck at the bottom, you should check to see if it is alive first. Even if you have noticed buoyancy issues, it is possible for the effects of swim bladder disorder to kill the fish.

On the other hand, if you have not noticed any buoyancy disorders, you will need to take immediate action if your fish is still alive. The least invasive way to check if your fish is still alive is to see if there is any gill movement.

Fish cannot live without breathing, so if they are alive, there will be gill movement. However, if is fish is injured or ill, the movement may be too small for you to notice. If you are unsure, take a net and gently move the fish.

If the fish feels stiff and does not respond, it is dead. On the other hand, if there is some movement, even very slight movement, your fish is still alive and needs your help. You will need to check your water parameters, so you should set aside some water and do an emergency 50% water change.

After the water change, test the water you set aside for ammonia, nitrite, and nitrate. If you register any ammonia or nitrite, that is the likely cause, or if your nitrates are over 40ppm.

Now take the number you measured and halve it. If the ammonia or nitrite is still above 0.25ppm or nitrates are above 40ppm after being halved, you must do more water changes until the compounds drop.


One of the largest issues with autopsies and necropsies that happen after a body is submerged in water is the fast rate of decomposition and possible scavenging of the body. If your betta lived solo, there won’t be an issue with scavenging, but there will still be an issue with rapid decomposition.

On the other hand, if your betta does have tank mates, whether it be feeder guppies, snails, a pleco, or anything else, the body will be consumed. Fish are incredibly opportunistic, and since the betta turned into food, they will eat the body.

Even if there are no tank mates, expect the flesh to disappear in 3-5 days and the bones to be gone in 1-2 weeks. Betta fish are very small, and it doesn’t take long for bacteria in the water column to break down their bodies.

This is a major issue in terms of determining what happened to your betta, especially in a community tank. If you are unsure as to why your betta died but it lived alone, you can simply sterilize the tank and move on.

However, if your betta died in a community tank, it may have been something contagious, so figuring out what happened is vital. It could have been anything from a bacterial infection to old age and examining the body shortly after death is a good way to determine this.

Where a Dead Betta May End Up

If you have only been away for a day or two and your betta passed away, you will still be able to find some remnants of a body. However, that body may be more difficult to find than you think.

When fish become sick, they will begin to isolate themselves from others and try to hide.

They also tend to become extremely desperate to hide and may wedge themselves inside of decorations. If this happens, they may get so stuck that their body won’t come out even if you shake the decoration.

When it comes to bettas, the first place you should check is the floor around the tank. Bettas are known to be jumpers, and if there is even a tiny space, they will jump out. The primary issue with finding the body depends on how many things are around the floor and whether or not you have a cat or a dog.

If your fish jumped and you have a cat or a dog that has access around the tank, there is a good chance that it ended up in their stomach. Dead fish smell, and that smell will attract your other pets.

Aside from decorations and the floor, another place to check is the filter. Take it apart entirely to ensure that your fish isn’t in there, alive or dead. If your fish wound up in there, you should put an intake sponge over the intake of the filter.

One of the last places to check is the tank substrate. Sometimes, and you may never find out why or how this happens, the fish may end up underneath the substrate. It is a rare occurrence for a betta to be found two inches under gravel, but it does happen.

Ammonia and Nitrite Spikes

Ammonia and nitrite spikes will occur after any fish death. The beneficial bacteria that convert waste (organic matter) to ammonia and nitrite and nitrate will begin to convert the fish’s body into these same compounds.

Since the body of betta has a lot more mass than the waste, the bacteria will not be able to fully process the compounds. This means there will be increased ammonia for a week or so followed by increased nitrite for a week or two followed by a nitrate spike.

If your betta died in a community tank, this is much more of an issue. You will have to do a lot of extra water changes once you remove the body. If your betta lived alone, you should do a 100% water change at the least.

In conclusion, most dead betta fish will not float. They will probably end up somewhere you would least expect it, but finding the body is very important. Otherwise, the dead body will cause lethal ammonia and nitrite spikes. This, in turn, can compound the problem, as the ammonia and nitrite spikes can kill more fish, which would lead to further ammonia and nitrite spikes.

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