So, your red eye tetra is showing a lot of aggression towards others in the tank? There are a few reasons why red eye tetras will be aggressive in an aquarium. Most of the time, it’s to establish their territory. Other reasons include mating, overstocking or a wrong male-to-female ratio. To prevent aggression, here’s what you need to know and how you can fix it.

As there are multiple reasons for this aggression, it’s important to go through all the most common options first.

What Makes Red Eye Tetra Aggressive?

Because there can be many reasons for this happening in the tank, you first need to find the source of the problem.

A common reason for red eye tetras showing a lot of aggression is to establish their territory. It’s normal for more aggressive species to fight for a part in the aquarium they call their own.

This usually happens if the red eye tetras have recently been introduced.

Lack Of Food
If you’re feeding your fish daily and believe you’re providing enough food, this one will most likely not be the reason why your red eye tetras are aggressive. Although if you don’t provide your tank with enough food, they will fight over it, with the aggressive fish turning into bullies.

Taking territorial behavior to another level, a red eye tetra couple will do anything to protect their eggs and fry. They’ll start by looking for the perfect spot to spawn. Once they’ve found their spot, they won’t allow other fish near it.

If you see a pair of red eye tetras in your aquarium, chances are high that you’ll see them chasing away other fish. As long as your aquarium is big enough and there’re enough spots to hide, this form of aggression will be harmless.

Overstocked Or Understocked
Overstocking could be the likely problem causing red eye tetras to be aggressive. If your aquarium has way too many fish in them, it’ll struggle to find their own territory. This can often result in the fish constantly fighting over space. You need to make sure that your aquarium provides enough space for your red eye tetras and any other fish in the tank. There should also be objects added to the tank that break the line of sight.

Useful items to use to help break the line of sight include rocks, plants and wood, which help to give your fish a break so that they won’t see each other constantly.

Male Female Ratio
If you have 1 female for every 3 males in your aquarium, the males will harass the female till she dies. This is unpleasant to watch and just not the way to go.

Instead, red eye tetras require a ratio of around 1 male to 3 females. This way, each male will divide his attention and won’t harass the females as much. This is important to keep a peaceful aquarium.

Spotting Aggression In Red Eye Tetras Early

The key to maintaining a peaceful tank is by spotting aggression early on before things get out of hand. Spotting the signs early will allow you to make the necessary changes before it is too late and before the red eye tetras kill each other.

Ways To Prevent Aggression

So now, the most important part: how to prevent red eye tetra aggression.

Adding Fish
If there is only one red eye tetra that harasses other fish in the tank, adding two or three red eye tetras can help as a distraction, as they’ll turn their attention to their own kind.

This is where adding more red eye tetras might be the solution. Also, as red eye tetras are schooling fish, the bigger numbers should reduce aggression.

Removing Fish
If there is one red eye tetra in the tank, that’s causing most of the aggression, giving that fish a “time out” in another separate aquarium has proven to work for a lot of people. Although we aren’t sure why this works, it defiantly works. Remove the red eye tetra for a couple of days to a separate tank and introduce it again.

If you’re housing a group of red eye tetras, you may see an obvious victim. When all the other red eye tetras are turning against one weaker fish, remove the victim for its own safety. You should try to find it another tank, whether this is with another enthusiast or back to your local fish store.

We’ve covered a variety of reasons for red eye tetra aggression, just like humans, sometimes there is no specific reason. Some red eye tetras will just not like each other. If this is the case, then simply removing one of the two parties is your best option.

Rearrange Aquarium
If your red eye tetras are fighting over territory, first of all, make sure your tank is not overstocked. If this is not the case, rearranging the aquarium may just do the trick.

The red eye tetra may not know the borders of its territory and it might cool down.