Why Are My Neon Tetras Disappearing? (How To Prevent Disease)

Tetras are very sensitive to their environment, even a slight change in the aquarium can be harmful to them. The reason your Tetras disappear, maybe because your neons live with other types of fishes that eat them. You will not notice this unless you are watching your fish tank 24 hours a day, so then you can see how your neons vanish. 

If you have time to keep watch over your neons, you will also see them having difficulty swimming and mostly staying at the bottom, and will slowly die once they had some illness or there is a change in pH, ammonia, nitrate in the water’s composition. Ensure that you always have the right level of each so your neons can survive. 

Problems with neon tetras that you may encounter

The highly sensitive neon tetras can encounter a few obstacles in the aquarium, including:

Neon Tetra Pleistophora Hyphessobryconis Disease

This organism can cause Neon Tetra disease. The disease is transmitted when an infected fish was eaten by the healthier fish. Once the disease progresses, cysts will start growing in the infected fish and begin to deteriorate and eventually die. 

Symptoms you should watch out for are the changing color of your neon will appear to have difficulty in swimming or curved spine for more advanced infection. 

You will also notice restlessness with your neons in the tank, or sometimes an infected neon will not swim with other inhabitants in the tank. They will also not swim in a controlled manner, but swim unevenly.

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Another indicator is the fin’s color cause lightening, or discoloration is appearing on their fins. There is also the danger of a second infection called bloating of the infected neon, or their fins will start to rot. 

This disease is highly communicable and can spread to the whole fish in the tank. What you can do is to check the performance of your fish and if there is any uncommon movement or isolation. Remove the infected fish fast so the other fish will not contract the disease. 

If you are not that much who examine your fish, it might be too late before you notice there is no more fish left in your tank as they all disappear.

How Do You Prevent Diseases of Neon Tetras?

Only purchase from reliable aquarium fish keepers and make sure that you are only buying healthy neons cause once you mistakenly buy one that has the disease, there is a danger that other fishes in your tank will also have it. 

When you go to the shop to purchase, check the aquariums or the tank where they are keeping the fish and avoid tanks that have sick or dying fish on them. A dirty or unkempt tank is also a no-no cause this is an indicator that the keeper is not careful in raising the fishes. 

Once you get your new neons, it is ideal to have them separated for at least a week before you place them in the same tank as the other healthy fish. This will ensure that your neons are not a carrier of the disease. 

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This is also the best time for you to observe your tetra’s appearance and their behavior while in the tank. 

What to Check Out For in Establishing Your Neons

Water Chemistry

You should have a test kit to check the right level of ammonia, nitrate, and nitrite before you place your neon tetras in the tank, there should not be more ammonia since this is a sure-fire way to kill your tetras. The water should have beneficial bacteria to start the nitrogen cycle, as it will take a few weeks before you have a naturally occurring nitrogen cycle. 


It is stressful for neon to have an unsuitable water temperature. It should not be too cold or too hot for them to get used to it. They can also get a temperature-induced shock for poor water temperature. 

The ideal heat inside the tank should be between 72 to 76 degrees Fahrenheit.

The School of Fish

Your neons will thrive if they have a fish school cause they also need companionship. They can have five or more companions, and there is a better chance your neon will grow healthy. 


Do not overfeed your tetras nor starve them. Get feeding supplies that your neon will like, and do not just feed them whatever you see in the market. Feed them color flakes, tropical granules, aqueon tropical flakes, or shrimp pellets. They can eat once or twice a day as young adults, but feeding should change as they mature. 


Provide your neons with various spaces where there are plants in one area and have the other area open for swimming. Having plants as cover will give them space to hide or to dart when they feel threatened. 

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You can opt for Brazillian pennywort, Vallisneria, Ludwigia repens, and Cabomba. Other plants you may choose are frogbit, red river floaters, or dwarf water lettuce. Live plants are better compared to the artificial decor since live plants remove nitrates from the water. 


Although tetras come from blackwater environments, they can thrive, as well, with dim lights but not bright ones. Neon tetra eggs are very sensitive to light, but if you have plants as decor under the tanks, then it can easily diffuse the light that the neons are getting and provide just the right shade for them. 


Though this will be used more when your neon would like to hide behind the castle decor or caves, these won’t matter much to your neons, but it is more of an aesthetic if you want to add one or two decors in their territory. 

So, are neon tetras just disappearing in your tank, or is there something more sinister happening underneath? Well, your neons may not be thriving as much as they should in your aquarium, and you are not just noticing them being eaten by other types of fish. Neons can thrive and grow in your tank if it is an already established tank that is perfect for their living environment, and you can enjoy them for a long time. You can also breed them if you like, so you’ll have plenty of beautiful neon swimming in your tank.

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