Tetras are one of the most popular freshwater aquarium fish— and for good reason! These fish are hardy and beautiful. They also do well in species-only and community tanks.
With so many benefits, it’s no surprise that many owners want more than one species. And luckily, different tetras can school together! Well… sort of.
Different tetra species will form schools and swim together. However, individual tetra will not join a school of another species. Because of this, you need at least six members of each tetra species.
When you begin mixing tetra species that are different sizes or have slightly different behaviors, this becomes especially important. But if you have enough tetras to form a sizable school for each species, they’ll all swim together.
Keep reading to learn more about the different types of tetras, if they’ll school together, and what factors play into this behavior.
In general, different species of tetra will not form one large, integrated school. Instead, each different species will form its own schools and then swim together.
Occasionally, this results in some intermingling. But on the whole, each species of tetra will remain with its own kind.
This is not absolute, however. Tetra may join the school of a different species under specific circumstances. For this to happen, the following must occur:
- The tetra must be alone or part of a species group that is too small to form a school
- The receiving school of tetra must be similar in size, color, and behaviors
If these two conditions are met, it’s possible for two or more species of tetra to form one school.
For example, this behavior has been observed with neon tetras and cardinal tetras. The two are very similar, so they have accepted members of the other species into their own schools.
Aquarists should keep in mind that this is not ideal or a desired outcome. If different tetra species begin forming one school, it means one species is lacking in members.
Individual tetras or tetra groups without sufficient schooling numbers suffer from increased levels of stress, are more susceptible to diseases, and have higher mortality rates than tetras in a large school.
So, if you see this happening in your tank, look for underlying causes that may be prompting your tetra schools to integrate.
Types of Tetras
There are many different types of tetras. In fact, over 30 species currently exist. Most of them have similar needs, but some have been bred to require very different water parameters.
For example, tetras are by and large tropical fish and need warmer waters. But, there are some species that actually enjoy cooler waters.
Below is a list of some of the most common types of tetra that can be housed together and form schools:
- Neon Tetra – One of the most recognizable species, this red, white, and blue fish gets along with almost every other type of species.
- Cardinal Tetra – Almost identical to neon tetra, these fish are similarly easygoing and great to stock with other types of tetra.
- Ember Tetra – These fish are easygoing, enjoy warm water, and are great for beginners; they’re named for their orange hue, despite being almost see-through.
- Bloodfin Tetra – With an iridescent body and red fins, it’s easy to see how these fish got their names. Their laidback disposition also makes it easy to see why they’re popular.
- Rummynose Tetra – Clocking in at 2.5 inches, this species is a bit larger than others; but even so, it’s peaceful and does well in community setups.
- Lemon Tetra – These tetras don’t have the traditional tetra body shape but are the same as others in terms of their temperament and behavior.
There are also many sub-varieties of the Neon tetra that aquarists are attracted to, such as the Green Neon Tetra and Black Neon Tetra.
Check out these different types of tetras and see if any of them are right for the tank you’re planning or already have.
Things to Consider
Body type and size are two of the easiest indicators of what species to keep together. Many species are known for being opportunistic fin nippers, so long-finned, slow, or small fish may be picked on.
For this reason, Blackskirt Tetras, Congo Tetras, and Black Phantom Tetras should either be kept together or introduced into a tank with other species with caution. All of them have longer fins that may make them a target for Neons or Cardinals.
Similarly, larger species such as the Mexican Tetra (4 inches), Bucktooth Tetra (5 inches), and Congo Tetra (4-5 inches) should be strictly monitored if housed with species that grow to two inches or less.
The biggest factor that affects school is the number of tetras you have— in this case, more is always better.
You need at least six tetras to form a school, but this is the absolute minimum. To really encourage schooling, a dozen or more is better.
The more tetra you have in your tank, the closer they’ll stick together and school.
This goes for each species of tetra you want to keep in the tank. You should try to stock at least a dozen Cardinal Tetra, a dozen Neon Tetra, a dozen Ember Tetra, etc.
Besides quantity, you also need to think about quality. Tetra will display more natural behaviors (i.e., schooling) in tanks that mimic their natural habitat.
Regarding their tank, this means that:
- Water Parameters – The water parameters need to be correct and meet the needs of each species of tetra.
- Tank Size – There needs to be ample free space for swimming and schooling; the more cramped tetras are, the less they’ll school.
- Tank Décor – Besides free space, there also needs to be places where tetras can hide, rest, and even mate.
- Community Fish – If you have a community aquarium, tank mates should be similarly peaceful fish that won’t chase or hurt the tetra.
If you make sure to meet these parameters, your tetras should be schooling easily and often.
Remember to do regular health checks and chemical testing. Tetras are hardy, but they’re not invincible. And their close-knit nature means that if one tetra becomes sick, more are likely to follow.
How to encourage schooling behavior
For the most part, you shouldn’t have to encourage schooling behavior. This is one of the most natural and strongest instincts that tetras have, present even from the moment they’re born.
But if your tetras aren’t schooling, it’s likely due to one of the factors discussed in the section above. To encourage schooling behavior and other natural habits, try running through this checklist:
- Do I have enough tetras? Make sure you have at least six, but preferably a dozen or more tetra of each species.
- Are my tetras getting along? Observe the behavior of each school; take note if one school is antagonizing another.
- Are my water parameters correct? Check the chemicals, water temperature, filter, and other equipment to make sure everything is balanced and in working order.
- Is my tank big enough? Take a critical look at your tank and see if it’s big enough. For multiple large schools, you should have at least 30 gallons.
- Is my tank set up correctly? Make sure you have ample free swimming space so the tetras can spread out if desired.
- Do I have enough cover? There should be rocks, driftwood, décor, plants, or some other type of cover in your tank.
- Are my tetras safe? Besides the threat of other tetras, you should also make sure your tank is free of predatory or aggressive fish.
When trying to encourage tetra schooling behavior, the tank and tank inhabitants are the two factors you’ll need to most closely examine.
If your tetras aren’t schooling, the answer likely lies in one of the questions above. Run through this checklist and make sure you’re able to answer ‘yes’ to each bullet point.
It’s also wise to check the health of your fish. Though there are likely to be other symptoms besides a lack of schooling, it may be that one or some of your tetra are feeling under the weather.
Tetras are gorgeous fish with a variety of different species to choose from. Besides this, they can also handle a wide range of tank environments and are extremely fun to watch!
Part of what makes them so captivating is their schooling behavior. They gracefully zip from one end of the tank to the other, forming patterns and fascinating onlookers.
If you can’t decide on just one species to own, you’re not alone. But you are in luck, because different types of tetra can school together as long as they have enough members of their own species.
And, of course, as long as the aquarium is properly set up for tetras. Thankfully, tetra tanks are fairly easy to set up.
With a few checks and changes, you’ll be able to watch different tetras school together in no time.