Why Are My Neon Tetras Fighting?

Neon tetras typically fight each other when they’re distressed. Issues with tank size, water quality, and food availability can stress your neons out and cause them to take it out on each other.

If your tetras are all getting along one moment and nipping at each other the next, it’s not a simple dispute between tank mates. Something in the water is probably riling them up, and you need to find out before it’s too late.

Don’t worry, though. Here, we’ll run through the probable reasons your neon tetras are fighting and give you some advice on how to stop them.

Why Are My Neon Tetras Fighting?

Neon tetras are a highly social fish species. They’re always among the top picks for community aquariums because they are mild-mannered. It’s almost a rite of passage for any fishkeeper to have neon tetras in their tank.

However, these popular peacekeepers can sometimes go beyond the usual fin-nipping and competitive mating behavior and get into real fights. When that happens, there are some factors you need to consider.

Neon Tetra

They’re Stressed Out

Stressed-out fish are prone to parasites, disease, and behavior problems. That’s why there’s likely a direct connection between your neon tetras’ distress and their aggression.

Below are some common causes of stress in neon tetras that you should look into.


Fish need well-balanced diets, too! And they need enough food to go around. Sensing food scarcity in any way can make them single each other out as threats.

Neon tetras are omnivores and need higher protein content in their flakes, with live or freeze-dried natural foods as dietary supplements. Make sure you’re able to feed them regularly to keep them happy.

Tank Conditions

Neon tetras are tropical freshwater fish and thrive best in a tank that mimics their natural habitat. Otherwise, they will have a hard time acclimating properly.

This means keeping them in a mature, fully cycled aquarium with the following conditions:

  • Temperature: 72F to 76F
  • Acidity (pH level): 6-7
  • Water hardness: below 10dGH
  • Minimum tank size: 10 gallons (5-6 fish)

Water Changes

Sudden water changes can be very stressful for neon tetras. While regular, partial water changes are all well and good, changing more than 50% of the tank’s water at once can trigger some neons to act hostile.

They’re Establishing the Pecking Order

Your neon tetras may also be fighting to establish dominance and optimize their position in the pecking order. A 2021 study using a fish-robot hybrid school found that neon tetras have preferred placements in their swim group according to different factors.

In general, most fish prefer to stay in the back, relying on the ones at the front to alert them against predators. Then, during feeding, they will want to be as close to the food as possible.

Especially when there are new fish in the group, you might see your tetras getting a little aggressive as they herd each other into the formation they think is best.

They’ve Got Shoaling Problems

As a schooling species, neon tetra shoals are breathtaking to look at with their neon blue streaks and vivid red stripes. But, as we mentioned, their grouping behavior is more than just for show.

Keep only a couple of fish in the tank, and their heightened fear of being detected by predators will make them turn on each other. Keep too many, and the increased competition for food and mating partners will do the same.

That may be the reason they’re fighting each other.

How to Stop Neon Tetras from Fighting

Unfortunately, a dip strip to test for stress levels in your aquarium hasn’t been invented yet. Until then, you can always try the following methods to bring those stress levels down and prevent even more fights from breaking out.

Get a Larger Tank

Keeping tetras in a tank that’s too small for them is never a good idea. The lack of space and degraded water quality leaves them no choice but to panic and attack each other.

As a rule of thumb, it’s recommended to go up a gallon per inch of fish. If you include equipment and decor, you should have about 3 gallons of water for each neon tetra in your tank.

Maintain Good Water Quality

Test your water regularly to maintain the proper levels and water chemistry. Generally, larger tanks keep the quality up for longer, meaning you won’t have to make water changes as often. This is another good reason to size up your tank.

Give Them Lots of Coverage

Some good news for avid aquarium decorators: neon tetras need less open water than you might think. They’re used to natural elements surrounding them at all times.

Adding more plants and decor helps break up the line of sight for fighting neons and provides spots for them to weave into and retreat. Some good examples:

  • Moss
  • Rocks
  • Dwarf water lettuce
  • Frogbit
  • Cabomba
  • Vallisneria
  • Driftwood

You can also use fake plants if you’re so inclined. As long as they’re tall or floating, your neons are sure to love them.

Two Neon Tetras

Increase Their Numbers

Group size in tetras greatly affects their behavior. They’re known to be less erratic and aggressive in larger groups.

Additionally, you may notice them swimming more freely and eating more actively (e.g., coming up to the surface and competing for food).

Five or six fish in a single tank is the absolute minimum, but you should have more success with at least 8-10 tetras in a group. As long as the tank can support the population, your tetras will appreciate the added company.

Choose Compatible Tank Mates

Now that you have a sizable school of neons in your aquarium, you should also make sure to shack them up with the right tank mates. Their fellow tetras are all pretty good choices, but if you’re looking for a more diverse community, here are some ideas for you:

  • White cloud minnows
  • Danios
  • Cory catfish
  • Otocinclus catfish
  • Dwarf gouramis
  • Nerite snails

It’s best to stick with other schooling species and avoid larger fish that might just end up eating the neons. When in doubt, you can always ask your local specialist for recommendations.

Finally, Some Peace

All your neon tetras have is you and each other. So even though it can seem dire when they fight, there’s still plenty you can do to help them out.

Start with the right tank conditions and the appropriate number of fish, and go from there. With luck, they’ll be back to the hardy, peaceful stunners we all know and love.