Why Did My Neon Tetra Disappear? (With 6 Prevention Tips)

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So many times, I was amazed to find that my neon tetras got missing. That happened with other fish as well, although, with tetras, it happened too frequently. Over the years, I’ve learned a few reasons that cause tetras to disappear and found how to deal with them. Now, I am willing to share my experience.

Neon tetras typically disappear and go missing due to stressful conditions, including aggressive tankmates, diseases, and inadequate water parameters. These will force tetras into hiding behind rocks, plants, and decorations. However, it is also possible that the tetra died or got eaten by other fish.

As we move forward, I will share a few more reasons that may be accountable for your missing tetra. I will also show you what steps you should take to avoid that in the future. These will also prevent other fish from disappearing.

Also Read: 15 Things You Should Know About Neon Tetras

Why Are My Neon Tetras Disappearing?

People always panic when their fish disappear and for a good reason. Tanks are limited in the amount of space they offer, and fish have nowhere to go. For that reason, the disappearance of a fish is often a source of concern.

If one or two fish can disappear, you cannot help but worry that more fish will disappear in the long run. This is why it is essential to find out why your fish disappeared in the first place. That way, you can resolve the issue before you lose more fish.

If you are one of those aquarists whose neon tetra numbers keep falling, one or more of the following factors is probably to blame:

1. Your Neon Tetra Is Hiding

Aquarists that cannot find their fish tend to assume the worst. But in many cases, your neon tetras are merely hiding. Fish can hide for any number of reasons, including:[1]

  • Stress – This is one of the most common causes of missing tetras. It is also the reason why neon tetras like plants and decorations. They can use these objects to stay out of sight during stressful periods.

Also Read: Stress In Neon Tetras

  • Aggressive Tankmates – Neon tetras grow to an average size of 1.2 inches and are therefore considered relatively small. As such, bigger fish tend to prey on them. Aggressive tankmates can create a hostile environment in the aquarium. Naturally, the neon tetras will respond to that hostility by going into hiding and staying there until the threat is removed.
  • Disease – Sick fish do not feel safe out in the open. They are weak, sluggish, and mostly incapable of defending themselves against violent tankmates. For that reason, they will find a safe place to hide until their health improves.

Also Read: 17 Neon Tetra Diseases & Their Treatments

  • Recent Transition – New fish are also hesitant to stay out in the open. If you have just introduced your neon tetras to a tank, the fact that you cannot find them shouldn’t surprise you. They are probably hiding in some nook, trying to make sense of their new surroundings.
  • Numbers – Neon Tetras are schooling fish that should be kept in large groups. If you force them to live alone or in small groups, they will remain hidden because they don’t feel safe or comfortable.

Before taking any drastic steps, try looking for your fish in, around, under, and behind the plants and decorations. Look under the rocks and in the substrate. Check every corner of the tank before you conclude that your neon tetras have disappeared.

Don’t forget that neon tetras lose their color when they are stressed. That could also happen when they are sick. In some cases, they lose so much color that they are practically transparent.[2] This can make finding them a nightmare.

Also Read: Why Do My Neon Tetras Keep Hiding?

2. Jumping Neon Tetras

If you are new to aquariums, it might shock you to learn that fish can jump out of their tank. They will use any opening they can find. And because they can’t breathe outside the water, any successful escape on their part will end in death.

Depending on your aquarium location, it may take you a while to find a fish that left the tank. They do not always land out in the open. Some might slip between the tank and the wall, while others may fall into the nearby cabinets.

The reasons that may compel a neon tetra to jump out of the tank will vary. They include:[3]

  • Bullying Companions – If aggressive tankmates are harassing a neon tetra, it may attempt to escape by jumping out of the tank. That is quite prevalent in tanks that feature fast swimmers, such as mollies and guppies.
  • Low Water Conditions – As was mentioned before, neon tetras are sensitive to poor tank conditions. High temperatures, the wrong pH, overcrowding, and elevated ammonia concentration could compel a neon tetra to jump out of the tank.
  • Curiosity – Some neon tetras are just curious. If your tank doesn’t have a lid, they may leap out to explore the world outside the tank. I will say that fish are not the most intelligent creatures. They do not necessarily know that the world outside the tank is bad for them.

3. They Got Missing During Cleaning

Typically, I encourage aquarists to vacuum their gravel. This is the only way to prevent the leftovers and fish waste that fell in the gravel from rotting and increasing the concentration of ammonia in the tank. 

However, because neon tetras are so small, you may have accidentally sucked them up without realizing it. They could have also gone missing during water changes, in which cases aquarists typically pour the dirty water into the sink or toilet.

4. The Neon Tetra Is Dead

Strangely enough, aquarists rarely consider this. After all, if their neon tetra was dead, they would see it in the tank. Regarding that topic, you have to keep three factors in mind:

  • Tankmates – First of all, fish will eat whatever can fit in their mouth, and that includes other fish. If your neon tetra dies, because it is so small, the other fish in the tank won’t hesitate to eat it, and they are not the only ones. Snails don’t attack living fish. However, they are more than capable of eating dead fish. In other words, if your neon tetra dies, you may never find the carcass. You won’t even know that it died, not for sure.
  • Cannibalism – As was noted above, fish will eat anything that can fit in their mouth. Not only will bigger fish eat a dead neon tetra, but they won’t hesitate to eat a living one either. If you can’t find your neon tetras, you have to consider the possibility that the other fish ate them.
  • Hiding – It takes some aquarists days and even weeks to find the remains of dead fish. Don’t assume that the carcass of a dead neon tetra will float to the surface of the tank. It can become lodged in the filter. The current could slip the carcass between some rocks. 

Also, bear in mind that fish lose their color when they die.[4] This makes them even harder to find. Fish can die for any number of reasons. Like other species, they are quite sensitive. They require specific conditions in the tank. Otherwise, their health will suffer.

5. Your Neon Tetra Is Sleeping Somewhere

Neon tetras, being small and brightly colored fish, tend to sleep in hidden, darker spots in the aquarium to avoid predators during their nocturnal rest period.

The crevices in rocks, dense patches of plants, or even under the aquarium substrate are ideal hiding places for them to retire at night.

This natural behavior can make them appear to be missing when they are, in fact, just asleep and concealed within the complex environment of their tank.

Also Read: Do Neon Tetras Sleep?

How To Prevent Neon Tetras From Going Missing?

If your neon tetras disappear, you should give them a few days. If they reappear, you have nothing to worry about. But if they fail to reappear, you must take steps to prevent more fish from disappearing. Some practical options include:

1. Improving The Water Parameters

If your tetras go missing occasionally, I recommend improving the conditions in the tank. Neon tetras require a particular temperature (72 to 76 degrees F), pH (6.0-7.0), and hardness (1 to 2 dKH).[5] The wrong parameters will induce stress, causing the neon tetras to either hide or jump out of the tank. 

They are also more likely to contract diseases, which can encourage them to remain in hiding. For that reason, you must maintain the right parameters in the water. If your fish are happy and healthy, they have no reason to hide or jump.

If you don’t own one already, I highly recommend getting the API Aquarium Test Kit (link to Amazon). That bundle will measure your pH, ammonia, nitrates, and nitrites pretty accurately. After testing numerous kits, I have no doubt you should get this one, mainly because it lasts for incredibly long periods.

In case you suffer from ammonia spikes, feel free to check an article I wrote where I discussed why ammonia remains high after water changes. I made sure to list all the possible steps to fight elevated ammonia levels.

Also Read: Neon Tetra Temperature

2. Conducting More Frequent Water Changes

Bear in mind that you should change the water in the neon tetra tank regularly. This is the only way to prevent ammonia and nitrites from killing your fish. You must keep the ammonia and nitrite levels at 0 ppm. 

Start by replacing 25-50% of the water weekly. Between changes, test the water for ammonia and nitrites. Also, make sure that the pH falls between 6.0 and 7.0. If you notice spikes, move to biweekly changes.

Anything higher will induce stress in the neon tetras, compromising their health and making them more likely to hide or jump. You should also keep the water clean. Do not permit leftovers, fish waste, or dead organic matter to stay in the tank. It will rot, ruining the water in the process.

Also Read: What Is The Best pH Level For Neon Tetras?

3. Vacuuming The Substrate

When it comes to cleaning the gravel in your tank, use special vacuums that have covers whose slots are big enough to suck leftovers and fish waste. However, make sure that they are too small to allow fish to pass. 

Some people place pantyhose on the vacuum, which achieves the same effect. It will prevent small fish like neon tetras from being sucked into the vacuum. Either way, explore the substrate carefully before vacuuming and make sure that it is fish-free.

4. Getting The Right Tank Size

Even though Neon Tetras are small, they still need a generously sized tank of at least ten gallons.[6] A single neon tetra can survive in just one gallon of water, but neon tetras cannot live alone. They thrive in large groups.

Therefore, you need a tank that is large enough to house a sizable school of neon tetras.

Also Read: Neon Tetra Tank Size

5. Consider A Lid

Make sure that you are keeping your aquarium covered. If your neon tetras have a penchant for jumping out of the tank, the only rational solution is to cover the tank. It would help if you also lowered the water level. 

Make sure to leave a gap between the surface of the water and the top of the tank. This will make it more difficult for the neon tetras to leave the tank, especially if you don’t have a lid.

6. Choose The Right Tankmates

Neon tetras are peaceful and must be kept with other peaceful fish such as Corydoras Catfish, Bristlenose Plecos, Guppies, Platies, and Cardinal Tetras. On the other side, please avoid large, aggressive fish like cichlids. 

If some of the peaceful species behave aggressively for some reason, you can either remove them or separate them from the neon tetras using a divider. If your neon tetras are new, the only solution is to give them time to grow accustomed to the tank. 

They will eventually emerge. It would help if you also made the tank as appealing as possible by adding plants and eliminating hostile fish whose presence might encourage the new neon tetras to remain in hiding.

Also Read: 19 Great Neon Tetra Tank Mates


If your neon tetra goes missing, your first step should be looking closely at your tank. That is because most of the time, the tetra is merely hiding. Check the rocks, plants, and decorations. If you failed to find it, explore the substrate.

If your fish died, it had probably sunk to the bottom. Bear in mind that dead fish typically lose their color, which is why you should look closely. Ultimately, if you cannot find the fish anywhere, consider the possibility that it had jumped out of the tank or got eaten by its tankmates.


  1. https://www.thesprucepets.com/why-do-my-fish-hide-all-the-time-1380775
  2. https://tetra-fish-care.com/neon-tetra-behavior-aggressive-fighting-or-playing/
  3. https://www.aquariumnexus.com/neon-tetra-jump/
  4. https://animals.mom.com/how-to-tell-if-a-goldfish-is-really-dead-8595027.html
  5. https://modestfish.com/neon-tetra/
  6. https://www.fishkeepingworld.com/neon-tetra/