Neon Tetra Behavior (Fighting, Hiding, Not Eating, Chasing etc.)

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Neon Tetra fish are a really popular species since they’re beautiful to look at and generally a pretty resilient fish. Beginner aquarium owners love them, and they’re a great introduction to setting up a proper tank with just a few parameters that you need to monitor.

But because they’re so hardy, that means you might be concerned if you notice a change in their behavior. Stress isn’t good for fish, it can make them more susceptible to illness and stop them from eating.

So, I’ve prepared this guide on some of the common changes in Neon Tetra behavior, and what the cause may be.

Why are my Neon Tetras fighting?

Generally, Neon Tetra are peaceful fish. If they are acting aggressively, it could be a sign that they are ready to mate, that they don’t have enough space in the tank, or that they’re not getting along with another species of fish in the tank.

It’s rare for these fish to act aggressively at all, so any signs of Neon Tetra fighting shouldn’t be ignored. They are playful fish though, that will occasionally chase each other and even nip at fins. Provided the nipping doesn’t become excessive, this shouldn’t be something to worry about.

Always check the conditions of the tank if you see signs of aggressive behavior starting. Do they have plenty of space to swim around? You should be aiming for at least a 30-gallon tank if you’re getting between 15 and 20 Neon Tetra fish. You can manage with a smaller tank if you have fewer fish, but it’s advised to have at least 10 fish, so they’re comfortable schooling.

Read more: Neon Tetra Tank Size

If the tank is a good size, and the water parameters haven’t changed, then it may just be mating season.

Male Tetra can start to act aggressively to try to win the female as a mating partner. If that looks like it might be the case, you can separate the potential mating pair into a separate tank to stop the aggressive behavior. Just be aware that a breeding tank has different requirements for water parameters than a community tank.

Read more: Neon Tetra pH and Water Parameters Guide

Do Neon Tetras hide?

Neon Tetras will hide when they feel panicked, or when they just need some time to relax. This is perfectly normal, and space should be provided to allow your Neons some quiet time when they need it – tall, leafy plants are excellent for this purpose.

Neon Tetra hiding only becomes a concern when it is excessive. Check – is there any reason that your fish might be stressed? Do they even have enough room to swim freely, especially as a schooling fish?

If all your Neons are spending most of the time hiding, check that the water parameters are right for them too. You should be testing the water at least once a week with an aquarium testing kit anyway.

I use API’s freshwater master test kit – check the price on Amazon

How do I get my Neon Tetras to eat?

Neon Tetra aren’t fussy eaters, so if they aren’t eating it’s usually a sign that they are full, or that they are stressed out either because their water parameters aren’t correct or something else is worrying them. Large pieces of food should be broken into small pieces to help.

The most common cause of Neon Tetra not eating is stress. Make sure you’re checking the water parameters regularly so that the conditions are right for the fish, and ensure they have enough space to swim freely, but also places to hide and relax.

This quiet downtime is important to Neon Tetras, but no more important than free space to swim.

Make sure they aren’t being bullied by any other fish in your aquarium too. If that’s the case, the only option will be to remove the bully into a separate tank.

If your fish still isn’t eating, then they may be sick. You can read more on the potential causes in my guide to Neon Tetra Disease and other illnesses.

Neon Tetra with Cottonmouth or Cotton Wool Disease

Is it normal for Neon Tetras to chase each other?

Neon Tetra chasing each other can be normal playful behavior – they are an energetic species. But it can also be a sign of showing dominance in a male-only aquarium, it might be a sign of mating, or it could be a sign of overcrowding.

Keep tabs on your fish if they’re chasing each other a lot. Look for other signs of behavior that might be more aggressive or signs that some of the fish are acting stressed because of the chasing. Make sure there’s enough space, with hiding spots too.

Sometimes Neon Tetra may nibble on other fish’ fins.

The occasional nibble isn’t a problem normally, but if it keeps happening then you may need to look at the causes. Make sure the fish have enough space, as it may end up causing damage.

Why is my Neon Tetra swimming erratically?

Common causes of Neon Tetra swimming vertically or other erratic patterns include stress, poor water quality, or sickness including ammonia poisoning. Check the water parameters using an aquarium testing kit.

Note: If you’re concerned about ammonia levels in your tank, read this guide to lowering ammonia quickly.

If the water parameters are right for the fish, then look at what else might be causing the fish to be stressed. Often it’s overcrowding or the presence of a bully fish.

Another potential cause is if the fish are mating. males may swim vertically to chase a female, or to show aggression to other males.

Look out for male Neon Tetra swimming in a square pattern. That’s a sign that they’re getting ready to breed.

Read more: How to breed Neon Tetra in a tank


How can you tell if a Neon Tetra is stressed?

Signs that Neon Tetra fish are stressed include a lack of appetite, unusual swimming style (including crashing against the bottom of the tank), swimming only near the surface of the tank, uncharacteristic aggression or spending more time than normal hiding among plants or other tank decorations.

Why are my Neon Tetras at the surface?

If your Neon Tetra fish are swimming at the surface, they may be showing signs of stress. Neon Tetra fish experience lower oxygen pressure when undergoing a stress reaction, and so will swim to the surface to gasp for extra air to balance it out.

What does a sick Neon Tetra look like?

There are various physical signs to look for in a sick Neon Tetra. Restlessness is a common sign, as is a loss of coloration, particularly in one area of the body. Check for lumps or cysts, any curvature of the spine, and difficulty swimming or a refusal to eat.

Why are my Tetras spitting out their food?

Fish often spit out food to break it into smaller pieces, so this may not be a problem. Some fish spit food out if they don’t like it, but Tetras eat almost anything. If a Tetra is spitting out small food, it’s likely stressed or unwell – check for other symptoms.

How do you know when a Tetra is happy?

Signs that your Neon Tetra fish are happy include them swimming freely and energetically around the whole tank, they have a vibrant glow to their scales, they don’t seem scared of other fish and they’re breathing regularly but not rapidly. They may hide occasionally, but that’s normal.

Are my Neon Tetras fighting or mating?

It can be hard to distinguish between fighting and mating in Neon Tetras, as males will get aggressive with other males during mating season. Separate mating pairs from the community tank into a breeding tank, and look for signs of the male swimming in a square pattern.


Neon Tetras are normally easy fish to look after. Provided you set the water parameters correctly, then they’re a hardy fish that will get along with most other species well.

This means you shouldn’t ignore any behaviors which seem out of the ordinary, as this usually means there’s a problem that needs dealing with.

I’m sure you’ll be keeping a close eye on your fish anyway, but I’d recommend you just track any unusual behavior and make sure to separate aggressive fish if you need to. Look out for signs of stress, and test your aquarium water at least weekly to make sure there’s been no shift in the parameters which could be upsetting them.

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