Freshwater Fish

Fallow Deer Tetra – Exodon paradoxus: Care Guide

Bucktooth Tetras are a unique and active freshwater fish that definitely stand out. These are not your typical tetra!

But their high level of aggression is something you should be aware of before you even consider having one for yourself. This species can be downright nasty!

This guide will teach you how to handle their feisty nature and how to prepare for all other aspects of fallow deer tetra care.

Species Summary

While the fallow deer tetra is part of the tetra family, it is nothing like the peaceful community the fish are most familiar with! Scientifically known as Exodon paradoxus, this freshwater fish is predatory and wildly aggressive.

Best for experienced aquarists, the Exodon paradoxus tetra can be violent with any other fish in the vicinity. They are one of several species that feed on scales from the Amazon River basin. Groups will swarm the fish and slowly rip their scales off!

Bucktooth tetras are found naturally throughout Brazil and Guyana. While not as popular as its peaceful cousins, this species is still available in the aquarium trade.

Revered for their beauty and fierce nature, they are considered a must-have for many aquarists!

Appearance of the fallow deer tetra

The crow’s tooth tetra is similar in appearance to other types of tetras. They are small, torpedo-shaped and very colorful!

The base color is metallic silver. However, the silver is embellished with hints of yellow, green and red. Two large spots accentuate the body as well. One is in the middle of the body and the other is at the base of the tail.

The fins are transparent with a hint of yellow. Red and orange spots cover the dorsal, pectoral, and anal fins. Meanwhile, brighter yellow flecks add a splash of color to the tail.

Despite their creative name, these freshwater fish do not have protruding teeth. However, his teeth are still quite unique. To help with the fish’s scale-eating habits, the teeth are pointed and quite sharp. They can easily get under tough scales to rip them off!

The teeth and lips are turned outwards, which allows them to damage and bite other fish. As threatening as it may seem, it’s actually quite difficult to see its teeth unless you look carefully up close.

Exodon paradoxus life expectancy

The lifespan of a healthy fallow deer tetra can reach more than 10 years. That’s pretty much on a par with other tetra species.

Like any other fish, Exodon paradoxus tetras need a well-cared-for environment and a proper diet to reach their maximum lifespan. Without quality care, these fish could suffer from disease and premature death.

Average size

The average size of an Exodon paradoxus tetra is around four to five inches when kept in captivity. However, they can get up to six inches long in the wild!

Author’s Note: Many aquarists have tried their best to get fallow-tooth tetras to reach the six-inch mark in captivity, but it rarely works. Even with massive tanks and elaborate feeding strategies, this freshwater species always seems to stay smaller when kept in an aquarium.

Bucktooth Tetra Care

Tetra fallow deer care is usually best reserved for aquarists with a bit of experience. These are truly remarkable fish with some very different behaviors and needs!

To be honest, they can be challenging regardless of your experience level. But with a little knowledge and dedication, caring for these fish should be manageable.

Here are the main care guidelines to follow!

tank size

First things first, you need a spacious tank if you want to keep these fish! For a group of 12 Exodon paradoxus tetras, we recommend using a tank that can hold no less than 55 gallons.

Author’s Note: Of course, a bigger tank is always better. This is especially true if you want to keep an even larger group.

If you think it’s pretty big for a relatively small fish, here’s why it matters:

Exodon paradoxus tetras are quite active and need ample space to swim and explore. Also, they are bank fish. You must keep a large group together to avoid infighting and cannibalistic behavior (more on this later).

water parameters

Bucktooth tetras are not too picky when it comes to water parameters. They do well in standard water conditions that suit the many South American tropical fish that exist.

In the Amazon River basin, the waters are warm and teeming with life. Thanks to the debris that covers the riverbed, the waters are also often acidic.

  • Water temperature: 72°F to 82°F (approximately 75 degrees ideal)
  • pH levels: 5.5 to 7.5 (aim for slightly acidic)
  • Water hardness: 0 to 15 KH

Author’s Note: Be sure to go out and get a reliable aquarium water test kit to help you monitor these conditions on a consistent basis. This will allow you to make adjustments and changes before any of the parameters slide to a dangerous level.

What to put in your tank

These fish are not crazy about using plants as a place to hide. They are too aggressive and active for that! However, they still prefer to have some vegetation that they can get through.

A mix of live plants can do these fish a lot of good. Opt for plants like java fern and Amazon swords. Grass-like plants in the foreground and some floating plants in the aquarium are also good choices.

But be sure not to overcrowd the tank with plants! Keep them around the perimeter to create a natural setting that still allows them to swim. Exodon paradoxus tetras are not known to harm plants, so they should thrive in an aquarium with this type of setup.

For the substrate, use a dark sand material. These freshwater fish like to stay in the middle and top of the water column, but may venture there in search of food. The sand is safe and natural looking.

Author’s Note: Additional decoration is also always a good idea. You can add driftwood, caves, and rocks. Like plants, don’t overdo it! Keep things simple and focus on providing an open space for swimming.

Common Potential Illnesses

There are no unique health issues to worry about with the Exodon paradoxus tetra. However, they can still suffer from all the usual ailments that affect other freshwater species.

These fish can get ich, suffer from bacterial infections (such as fin rot), or fall prey to parasites anyway.

The good news is that most major health problems are easy to avoid. Exodon paradoxus tetras are quite hardy, but can react negatively to large fluctuations in temperature or pH. A buildup of ammonia and nitrates in the water can also cause serious damage.

Maintain proper water conditions and be sure to use a powerful filtration system to keep the environment in good condition. Partial water changes every week or two are also important.

Food and Diet

Exodon paradoxus tetras are carnivores through and through! In the wild, their diet consists mainly of fish scales.

When they eat scales, a group will swarm their prey and attack from all directions! Actually, this is quite similar to a piranha.

It might take a second to get used to this unique feeding experience, but it’s not too difficult once you get the hang of it.

Many owners will provide live or dead feed fish to meet these requirements. You can also offer some other high-quality protein sources for the sake of variety. They readily accept brine shrimp, bloodworms, earthworms, and other insects.

Author’s Note: Some fish will even take commercial flakes, but don’t expect them to be satisfied with just flakes or pellets. To keep these fish healthy, they need protein-based food!

behavior and temperament

As we mentioned earlier, Exodon paradoxus tetras must stay in groups to really thrive. But unlike many other freshwater species, this is not a matter of anxiety or trust. When these fish are not in a large group, they are quick to attack each other!

There is no exact science to determine how many fish it takes to prevent this. But in general, groups of at least 12 are successful. If you have a very large tank, don’t be afraid to get a group of 25-50!

In large groups, a single fallow deer tetra will not be attacked or killed. Instead, they will band together and focus their attention on any other sick or unhealthy fish.

These fish can create a beautiful display of color when they swim together. Very active, they will slither around the tank to explore and exercise. They can swim in unison, but will also split up and do their own thing from time to time!

Exodon paradoxus tetras are a very aggressive fish that are also very confident in the aquarium. They are not shy like other tetras! As a result, they are always a joy to watch and one of the most entertaining freshwater species you can find.

Bucktooth Tetra Tank Mates

Due to their aggressive nature, Exodon paradoxus tetras do best in a single species tank.

While they are not the largest fish out there, a group of fallow deer tetras can easily take down and kill a larger fish. Any other fish in the tank will quickly turn to food.

Author’s Note: Even cichlids, known to be bullies in community tanks, will act like startled targets in the presence of Exodon paradoxus tetras!

These fish will make quick work of almost any fish. The worst part is that it happens quickly! It only takes a few minutes for another fish to be attacked by a hungry, scale-eating Bucktooth Tetra. Before you know it, the group will swarm and rip the fish apart.

Some aquarists have experimented with aggressive bottom-dwelling fish species. But even then, there are never any guarantees of safety. Even if a tankmate stayed away from the group, his health would probably suffer from all the stress.

So, in summary, it’s always best to keep Exodon paradoxus tetras in a single-species aquarium (no matter how confident you are in a potential tankmate combination).


Captive breeding of fallow deer tetra is possible. However, it is incredibly rare and quite challenging.

These fish are egg layers that do not show any signs of parental instinct. If you want to try your hand at breeding, it’s best to do it in a separate tank.

Set up a small breeding tank with similar water parameters. Add some fine-leaved plants. Bucktooth tetras are egg scatterers. The plants will offer some protection to the eggs.

Author’s Note: Alternatively, you can install a layer of mesh at the bottom of the tank. With the mesh, the eggs can fall out keeping them separated from the adults.

Condition your fish on a high-protein diet several days before you want to breed them. Then select a pair and move them to the breeding tank.

To start spawning, you can perform a 50 percent water change. Use water that is a couple of degrees warmer to simulate the changing temperatures of the breeding season.

If you are lucky, the female will spread her eggs throughout the tank. When this happens, remove the adults immediately so the eggs have a chance to survive.

The eggs will hatch in two to three days. Once they are free swimming, provide brine shrimp as food. Don’t be surprised if you lose some baby fish. They are prone to cannibalistic behavior, so their young population will decrease in number as they grow older.

The best thing you can do is keep them well fed so they don’t fight each other when they’re hungry.


Caring for the fallow deer tetra is primarily about learning how to handle the aggression of this species. If you don’t plan for this, chaos will quickly ensue in your tank!

But if you create an environment that minimizes aggression from these fish, they can be a joy to keep. You will be treated to a constant display of activity and color.

If you are still unsure about the possibility of owning this species, feel free to submit your questions! We are always happy to help our readers.

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