What to Do If Your Aquarium Fish Goes Missing

fish swimming in aquarium

At some point, every aquarium owner has realized that one of their fish has gone missing. The good conclusion is that the fish was responsible for something and reappeared quickly. Sometimes, though, the fish is never discovered. Why do fish go missing, and how can they go into thin air (or water)? When a fish goes missing, it's critical to track it down and figure out what occurred. If fish continue to inexplicably vanish, the need to figure out why is even more pressing.

Hiding Fish

Some fish species don't want to be out in the open. They will hide the most of the time and can come up with some extremely inventive out-of-the-way locations. They'll hide behind rocks, under ornaments, within plant clumps, and even bury themselves in the ground. So, before you conclude the lost fish has disappeared forever, investigate the tank thoroughly. You might be surprised to learn where fish hide. Even if you find the missing fish, you might be curious as to why they hide so often and what you can do to help. Fish hide for a number of reasons, ranging from fear of their environment or other fish to a lack of social skills. Nocturnal fish are active at night, but they will hide during the day or when the lights are turned on in the aquarium.

Jumping Fish

Another possibility for a lost fish is if it leaped out of the tank. Even though the tank has a cover, the fish can leap out if there are any holes. Sadly, when a fish jumps, it typically means disaster. The fish will perish and dry up unless you discover them immediately after the escape. When a fish goes missing, the first thing you should do is check the area surrounding the tank to see whether the fish leapt out. If the tank is on a stand, look behind it and inside the cabinet. Because the fish may crawl around in search of its aquatic home, the distance a fish may be located from the tank is quite vast.

Surprisingly, certain fish species can survive for lengthy periods of time outside of the water. Fish with a can live for a long time and can be rescued if discovered in time. Return any fish you discover outside the tank that hasn't dried up to the tank. Keep an eye on the fish to see if it comes back to life, and add some stress coat to the water to help repair the that has been destroyed during its "outdoors" journey.

If the fish survives, it will be more susceptible to disease for a while and should be regularly monitored for signs of sickness. Keep an eye on how the other fish react to it, as tank mates are known to prey on vulnerable fish. If necessary, place the sick fish in a or use a breeder net to keep it isolated from the other fish while it recovers.

Sick Fish

When a fish becomes unwell or agitated, it will usually hide. Finding a sick fish lurking in plain sight may be your last chance of discovering its illness and treating it before it dies. If you're hunting for a lost fish, investigate the filter intake since sick fish might become very weak and get sucked into the filter intake. The prognosis is bad in certain circumstances, but it's best to identify them before they die and spread the sickness to their tank mates, who would most likely consume them. If you locate a sick fish, isolate it in a different tank until you can treat it. This serves two purposes: one, to protect them from other fish, and second, to allow you to cure the condition they're suffering from with drugs in a smaller, barren quarantine tank.

Dead Fish

Dead fish, obviously, do not swim. When one of the fish in the tank dies, the other fish in the tank begin eating on their former companion. It's not about you; it's about nature. Don't jump to the conclusion that they killed their former tank buddy. They're simply taking advantage of the opportunity to eat something new. If the body of the deceased fish is not discovered quickly enough, the entire body may be devoured, leaving no sign of the missing fish. A unexplained fish disappearance is frequently caused by this.

If you're lucky, whatever killed the fish won't be passed on to the other fish. When a fish goes missing, though, it's a good idea to test the water for and nitrite to be sure nothing is wrong. There might be an illness present, or another fish could have turned bully and is preying on his friends. For the following week or two, keep a close eye on the other fish to ensure that none of them are exhibiting indications of disease. Keep an eye out for signals of hostility. It doesn't imply a fish can't become aggressive later if it isn't aggressive at first. Fish behavior can be affected by changes in the tank's population or simply shifting the decor.

It's also conceivable that the fish passed away due to old age. No fish lives indefinitely, and many fish have short lifetimes. Some of your fish may be nearing the end of their natural lives if you've owned them for a long time. Dead fish should always be removed as soon as possible, regardless of the cause of death.

Serial Disappearances

It may not be a severe problem if one fish inexplicably vanishes and is never discovered. Something is awry if one fish goes missing and is never discovered, followed by another and another. A variety of circumstances can lead to repeated fish disappearances. Water conditions, sickness, and even a bully who is murdering his tank mates are all factors to consider. Another option is that all of the fish are beyond their prime. When a bunch of the same species is acquired from the same shop at the same time, their ages may be identical. They eventually succumb to encroaching age, one by one.

Test the water for ammonia, nitrite, and pH if there are repeated disappearances. Compare the results to earlier tests to see whether there has been a change in pH or an increase in ammonia or nitrite. Any of these changes might cause the fish to become stressed, resulting in sickness and death. Look for any signs of illness, such as a loss of appetite, strange breathing, or unusual behavior. All of these things might be symptoms of sickness or stress, making fish more vulnerable to disease. Keep a close eye on the interactions between the fish to see if any are aggressive. If aggressive behavior is seen, the aggressive fish should be moved to a different aquarium or separated from the other fish in the tank using a divider. You've discovered the perpetrator if the disappearances halt.

Finally, if your fish are disappearing in a pattern, resist the desire to replace them right away. It's not a good idea to add additional potential victims to the situation until you figure out why the fish are disappearing.


"Got a Sick Fish? American Veterinary Medical Association.", "Disorders and Diseases of Fish. Merck Manual.", "Aquarium Water Quality: Nitrogen Cycle. Florida Department of Agriculture and Consumer Services." ;