Skip to Content

Are Cardinal Tetras Fin Nippers?

The various types of tetras are seeing a huge spike in their popularity right now and although they have always been a very popular fish, they just keep on increasing in popularity due to being so cheap, easy to find, and easy to care for.

Although aggression does tend to be low in most species of tetra, we do often see questions about how tetras will interact with their tank mates and more recently, we have noticed a number of people asking are cardinal tetras fin nippers?

With cardinal tetras being surprisingly cheap right now, we can understand why so many people are thinking of purchasing them to add to their aquarium.

It is great to see so many people reaching out and asking about how cardinal tetras will interact with their tank mates and if they are fin nippers too as it shows you are thinking about your other fish rather than just making an impulse purchase.

Due to so many people asking questions about if cardinal tetras will nip the fins of their tank mates as well as a couple of other similar questions, we have decided to publish this dedicated article on the topic.

Our hope is that we will be able to help any of our readers who are thinking of adding cardinal tetras to their tank with a goal of helping you understand the normal dynamic of the species in most tanks.

Are Cardinal Tetras Aggressive?

The majority of cardinal tetras are not aggressive and they will often just go about their business without paying much attention to their tank mates.

If your tank is too small or is overstocked then cardinal tetras can become stressed and anxious resulting in them nipping the fins of other fish or showing other signs of aggression.

Although cardinal tetras are very small, they are a schooling fish that do require room to swim so you really should be keeping them in a tank that is at least 10 gallon aquarium but we would highly recommend a cheap 20 gallon aquarium if possible.

This will offer enough room in the tank for a small school of cardinal tetras as well as one or two other fish species in the same tank while reducing the chances of them nipping the fins of their tank mates.

We usually recommend that our readers go by the one inch of fish per gallon in an aquarium so with a cardinal tetra coming in at around 1.2 inches when fully grown, you can keep around eight cardinal tetras in a 10 gallon tank.

This is usually the absolute minium we would recommend due to anything less than eight causing issues with schooling and potentially increasing stress and anxiety in the fish.

A 20 gallon tank can have between eight and sixteen cardinal tetras depending on any other potential tank mates you plan to keep.

“Paracheirodon axelrodi aka cardinal tetra” by vincent.limshowchen is licensed under CC BY-NC-SA 2.0. To view a copy of this license, visit

Are Cardinal Tetras Fin Nippers?

Cardinal tetras can nip the fins of the other fish in their aquarium but it does tend to be rare. If your cardinal tetras are nipping the fins of the other fish then this will often be due to having your fish in a tank that is too small or having your tank overstocked.

Some cardinal tetras will retaliate to aggression from their tank mates by nipping their fins too.

This means that the other fish you keep in the tank may actually have acted aggressively to your cardinal tetras first and your cardinal tetras are simply defending themselves.

Many people brand new to fish keeping will often keep cardinal tetras in tanks with unsuitable tank mates with the other fish potentially seeing the cardinal tetras as food so you also have to keep that in mind.

Another common mistake that we covered earlier is many people will try to keep their cardinal tetras in aquariums that are far too small.

Many people try to keep far too many fish in a tank that is just too small so you should try to go with a 10 gallon aquarium as an absolute minimum.

If you do go with a ten gallon tank then you should probably only be stocking it with cardinal tetras too with a maximum of eight cardinal tetras being kept.

How Do You Keep Cardinal Tetras from Fin Biting?

You are actually able to stop cardinal tetras from nipping the fins of their tank mates with it often being much easier than most people think.

Upgrading to a larger tank is almost always the best option though as issues with tank size is by far the most common reason that your cardinal tetras will nip the fins of their tank mates.

As we have covered below, a 10 gallon aquarium is the absolute minimum tank size we would recommend but a cheap 20 gallon aquarium is not that much more than most 10 gallon tanks these days.

Not only does a 20 gallon tank allow you to keep more cardinal tetras in it but it also offers the space to keep additional fish species in the tank too if you choose.

Many people will opt to keep around eight cardinal tetras in the tank while adding other fish to the tank. Depending on exactly what fish species you are trying to add, you may be able to have other fish species in a 10 gallon tank without issue too if they occupied different levels of the tank.

For example, eight cardinal tetras and one bottom dwelling fish will occupied different levels of water in the tank and rarely interact in a 10 gallon aquarium.

Will Cardinal Tetras Nip Betta Fins?

It can be common for cardinal tetras to nip the fins of any betta fish tank mates that they have.

This is often due to the tank that the fish are in being too small for their needs causing the cardinal tetras to be stressed and anxious and to nip the fins of the betta or causing the betta to be aggressive to the tetras and the tetras to then nip the fins in response to the aggression from the betta fish.

This is a very common mistake and we covered it in an article on keeping ember tetras with betta fish too.

People see the small size of tetras and just presume that they will be fine in smaller tanks and many beginners are not aware of how aggressive betta fish can be, especially male betta fish in a small tank with little to no space available for either species.

If you are wanting to keep cardinal tetras and a betta fish in the same tank without having problems with aggression or fin nipping then you really do need to be looking at a 20 gallon aquarium if possible.

A single betta fish along with between eight and ten cardinal tetras would be our recommendation for a tank of that size to try and minimise the chances of aggression between your fish.


That brings our article going over if cardinal tetras are fin nippers or not to an end. We hope that we have been able to help any of our readers who are considering getting cardinal tetras to understand that they usually do need a slightly larger tank than most people initially think. Thankfully, the smaller aquariums like the ten or twenty gallon tanks are much cheaper than they used to be so it shouldn’t be an issue for most of our readers to upgrade.