Do Aquarium Fish Play Dead?

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As a novice aquarist, you have plenty of mysteries to solve before creating a healthy, stable, and almost self-sustainable aquatic setup.

One of the issues you need to solve is learning your fish’s behaviors and temperaments.

The goal is to learn to distinguish between normal and abnormal behaviors. This will allow you to tell if your fish is stressed, happy, hungry, violent, uncomfortable, etc.

One such important behavior is the play-dead gimmick which many fish resort to.

But why and how can you tell whether your fish is just playing dead, sick, sleeping, or dead-dead? Let’s have a look!

What Fish Species Play Dead?

Several fish species can play dead, although most won’t. Interestingly enough, the play-dead mechanism isn’t a defensive tool exclusively. Some species, like Central American cichlids and some African cichlids, play dead to attract prey.

Parachromis friedrichsthalii (a species of Central American cichlids), for instance, looks like a decaying fish and tends to float upside down to attract potential prey looking to feast on its body.

Bettas also play dead when stressed or bullied by more aggressive tank mates. For the most part, though, the play-dead mechanism is more prevalent in reptiles and mammals.

It’s not so useful in fish, given that most fish species don’t discriminate when it comes to food. They consume it, whether dead or alive.

Do Goldfish Play Dead?

No, they don’t, although this is a common misconception among goldfish keepers. The reason for that is that goldfish are extremely messy fish, so they can produce a lot of waste.

This, paired with improper tank maintenance and overfeeding, can cause the fish to experience swim bladder disease, among other conditions.

Swim bladder disease impacts the fish’s buoyancy, causing it to float irregularly in the water. Some fish are unable to maintain their normal body positioning and can’t swim properly anymore, causing them to tip upside-down.

If you notice your goldfish swimming upside down or being unable to sink, consider moving it into a hospital tank for immediate treatment.

Swim bladder disease comes with additional symptoms such as an overly inflated belly, lack of appetite, lethargy, a curved spine, erratic swimming, etc.

Do Fish Float When They Die?

Yesn’t. In other words, it depends on how much time has passed since the fish’s death. Dead fish will sink immediately after death, so you will likely see them laying inert on the substrate, with their bodies moving slowly with the water currents. All fish sink when dead.

However, the situation will change fast as the decaying process sets in. The decaying process is nothing more than bacterial activity, with various forms of pathogens consuming the fish and releasing gases that fill the fish’s interior cavity.

Including the bladder. This causes the fish to swell up and rise to the water surface.

So, expect your dead fish to float 2-3 days after death. Naturally, you shouldn’t wait that long to declare your fish dead.

Decomposing fish will foul the water quickly due to the excess ammonia and nitrites produced during the decomposition process.

Ideally, you want to check on your fish regularly and investigate the problem more closer if your fish displays unusually lethargic behavior.

Is My Fish Sleeping or Dead?

Yes, fish also sleep during their rest hours, but they don’t close their eyes. This can cause some confusion among more inexperienced fish keepers, especially if they’re used to always seeing their fish active and swimming.

To check whether your fish is dead, dying, or simply sleeping, consider the following:

  • Check gill movement – It goes without saying that dead fish don’t breathe. If your fish’s gills don’t move at all, the fish is clearly dead.
  • Fin movement – Most fish move their fins slightly, even when resting. This is an automatic movement, allowing the fish to maintain its body position in the water. Dead fish don’t exhibit any fin movement.
  • Lack of reaction to stimuli – If you’re still worried and confused about your fish’s state, try to poke it with something. You have a problem if the fish doesn’t react in any way.

This is a good 3-step test to check whether your fish is dead or alive. But what about dying fish? Theoretically, these fish still exhibit physiological activity, so you might have difficulties diagnosing their state.

Fortunately, you can learn the differences between a sleepy and a sick fish quite easily.

A sick or dying fish exhibits lethargic swimming, lack of appetite, lack of interest in its environment or tankmates, hiding behavior, and various physical symptoms like:

  • Red skin patches
  • Foggy or unusually bulbous eyes
  • White cotton-like patches around the gills or mouth
  • White patches on the eyes
  • Red or bloody gills, etc.

In this case, proper treatment is necessary to improve the fish’s recovery chances. Euthanasia remains the sole viable option if the treatment doesn’t appear to work.

How Do You Know if Your Fish is Dead?

I would say that there are 3 major signs that your fish is deceased:

  1. Lack of breathing – We’ve already discussed this point and it’s the most telling of all. If your fish isn’t breathing, consider it dead. It doesn’t get any simpler than that. However, you may not be able to observe the fish’s gill movement, in which case you need to consider other markers as well.
  2. The eyes – Dead fish have sunken eyes and immobile pupils. Check the fish’s eyes with a bright light source. The fish is dead if the pupil doesn’t change shape or size. The pupil’s reaction to light is automatic, so the fish can’t control it.
  3. Pick it up – Your fish will react if you touch it or pick it up in your hand. If it shows no sign of physical activity, you have a dead fish on your hands.

Conclusion

Some fish species play dead to attract prey or deter predators, but this isn’t a common behavior in the fish world.

If your fish appears motionless or floats upside down, quarantine the animal and diagnose its condition. Especially if the species itself isn’t known for its play-dead behavior.

The fish is most likely dealing with a bacterial infection or a digestive problem, both of which have easy fixes, provided you identify the conditions in time.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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