Red Tail Shark

Red Tail Shark: The Ultimate Care Guide

The Epalzeorhynchos bicolor, red tail shark, or also known as the red-tailed black shark is more than meets the eye, or ears when you hear its name. You may be expecting a shark with a red tail, and you would be partly right. This little fish is not a shark but a freshwater fish that is part of the carp family.

They are indigenous to Thailand and are unfortunately they are on the endangered species list. They are sought after in the aquarium world due to their unique coloring. These fish possess a black body and red tail fins. They were thought to be extinct from 1996-2011 but have thankfully been confirmed as not. While they can’t be found in the wild, the redtail shark can still be seen in pet stores.

Care Level

They are not particularly difficult to care for, but aren’t considered beginner fish either. It’s not the little fish themselves that cause issues, but rather your choice of tank mates for these creatures, but more on that later.

In order to provide the right care, it’s worth it to note that the red tail shark is often confused with the rainbow shark. While we know what could cause confusion, there are some differences. The rainbow shark possesses red fins all around while the red tail shark (as its name would suggest) only has a red tail.

How they act and what they need will also differ from breed. For example, the red tail shark prefers faster water flow while the rainbow shark lives in slower streams.

Getting started on the right foot will also make sure your fish will grow to be healthy and strong. When picking out a red tail shark, make sure it is in good condition. Find one that has vivid color, is a strong swimmer, and shows no signs of distress.

Temperament and Behavior

Are red tail sharks aggressive?

Red tail sharks kind of go through a timid childhood phase. In the adolescent phase, it’s important to give them plenty of places to hide as they can be quite shy. We talk about lots of peaceful and non-aggressive aquarium pets here but the red tail shark is among the ones on the opposite side of the spectrum.

Do red tail sharks eat other fish?

The red tail black shark, another name for the species is quite territorial. They can become very aggressive if they feel like their space is being violated or impeded on. What makes them very special and interesting to raise is that they won’t necessarily attack their tank mates, but they use the very skilled method of tiring them out.

They will chase and “run up” on their opposition, and chase them around until they tire them out. They are considered bullies and would even intimidate other fish when it comes to feeding time. If you don’t spread the food throughout the tank and feed the fish too closely together, the red tailed black shark’s tank mates might suffer.

Just when you thought they discriminate against other species, you would be wrong. The red tail sharks adopt the “every man (or fish) for himself” mentality and also act out towards others of the same species. They are quite an active species and love to dwell near the bottom of the tank.

You will know something is wrong when they lose their energy level and seem more fatigued. They are often searching for food so feeding a few times a day, also so their tank mates can get some tasty morsels is a good idea. Also, try to keep the lid closed as these fish have been known to jump when startled.


Red tail shark surrounded by tank plants
The red tail shark is quite intimidating, consisting of two highly contrasting colors that add to their effect. They stand out with their bright red tails and dark black bodies. Their semi-aggressive behavior and being always on the lookout for food is partly why they earned their name. Another reason why the red tail shark is named this way is due to their dorsal fins.

They can get pretty big and max out at about 6 inches. Their lifestyle and feeding habits also contribute to their overall size. They are a small and slim fish that sort of resembles an underwater arrow. The way to tell a male and female red-tailed black shark apart is by looking at them after adolescence. It’s near impossible to tell many species of fish apart sexually until they reach maturity.

In terms of the red tail black shark, the females round out a bit as they mature. You will notice her abdomen is wider and more voluptuous, which is necessary for carrying her eggs. Again, keep in mind what we had mentioned above about the differences between the red tail black shark and the rainbow shark. While they are also different from guppies, there are some similarities in their skin.

Speaking of the difference of fins, when you start to notice that your red tail black shark’s red tail fin is lacking in color or dulling, you will know your little swimmer is stressed out. What’s also really interesting and slightly frightening about this awesome species of fish is their eyes. They have eyes that look like the dark abyss and match and blend in very well with their bodies.


It’s ones hope that their pets will remain with them for a long time. While we know that not a lot of smaller fish live very long, the red tailed shark is quite impressive in their longevity. These little fish, if taken care of well, can keep your tank lively for up to 6 years! Although there have been reports of certain red tailed sharks that live between 10-18 years of age.

However long you wish your little aggressor lives for depends largely on how well you take care of it. That brings us to the food and diet of these little creatures.


We know they fight for food so they will get plenty – we’re more worried about the other members of the tank. Let’s take care of the red-tailed black shark first. They feed mainly on plant life in the tank. However, they are omnivores which also means they eat insects, crustaceans and sometimes worms.

What works really well when feeding the red tailed shark is using flake or pellets. On occasion, they do enjoy the wonderful treat that is blanched vegetables, but just make sure you wash them first. Frozen fish food such as worms and brine shrimp will also go a long way in earning their affection.

They are also considered a scavenger species that won’t leave food untouched. However, when they do get full it’s important for you to remove all their leftovers to maintain water conditions. Since they are scavengers, they also help to keep the tank clean by grazing on algae.

Although they are omnivores, a plant-based diet is better suited to the red tail black shark and giving them more variety will be appreciated. Some professionals even suggest making your meals yourself if you want them to get the best of everything.


The Epalzeorhynchos bicolor is from the Cyprinidae Family like their carp cousins. So in actuality, despite their name, they couldn’t be further from the most dangerous predators of the sea.

Tank Conditions

What size tank does a red tail shark need?

This is where it really matters when it comes down to caring for your red-tailed black shark. Because they are such an active species, they require bigger tanks than most other fish their size. We’re looking at around 30 gallons or even larger for these strong swimmers. If you have other tank mates with them, then you may be looking at a 55-gallon tank.

As we mentioned before, these fish can jump when startled, so you need to make sure the tank is well covered. If you do want more than one red tail shark, then you need at least 5. If you only have 2 (thinking they’d be best buds), then you’re looking at fish that could run each other ragged and show aggression.

If you have a school of at least 5, they will have a pack mentality and you will see a hierarchy that doesn’t single any fish out. The ideal temperature of the water to simulate their native Thailand would be between 72-79 degrees Fahrenheit (about 22-26 degrees Celsius). The water hardness level should be around 5-15 dH.

The pH level needs to be slightly higher for them to be comfortable, around 7-7.5. Also, the red tail shark lives in rivers with fast water flow, so you need to do your best to mimic that as well. As for decorating the tank, use gravel or larger pebbles. They may mistake smaller pieces for food, so it’s important to make sure you use bigger pieces of substrate.

For plants, they are always a great addition, especially in their younger years when they are more timid and shy. They will hide about the plants and since they graze on algae, the plants will remain relatively unharmed in the tank.

Maintenance and Care

Clean out their habitat about once a week, and make sure you clear the uneaten food in less than two hours just to keep the environment safe. Also, try to keep the tank covered at all times with a weighted lid. Not only do the redtail sharks themselves jump, but they may trigger other tank mates to do so all in the effort to get away from them.

Remember that their tail fins become a duller red when they are stressed or when something is wrong. Since they are active fish, you can assume they may be sick, stressed or fatigued when they start floating around aimlessly and not keeping busy.

Other than making sure their energy levels are up and their tail fins are vivid, you also need to look at the condition of their fins. Make sure they don’t look shredded, frayed or have holes in them as this could damage their overall health. When they start gulping it can also be an indicator of illness.

They are relatively easy to care for on their own so if you are a beginner or are just looking into the red-tailed black shark, then we’d just recommend keeping one. Even if you are an experienced aquarist but lack the space, then we would still advise against having more than one of this species.

However many more red-tailed black sharks you add, the more space you need. As if having one wasn’t tough enough if it has tank mates, can you imagine more than one without the suitable allotted space?

Suitable Tank Mates

Don’t let all this information about aggression and bullying scare you away from introducing some friends to the red-tailed black shark. If you do it right, they can thrive with other fish. They are most aggressive when they find that their space is invaded or when they are trying to feed.

To keep the territorial aggression at bay, they need plenty of space. To solve the feeding issue, you need to put food throughout the tank and make sure you feed several times a day. As we also mentioned, they won’t attack other fish or harm them physically, they sure do a number on them mentally.

They set out to chase and chase the other fish until they eventually give in to the stress. Sometimes this even prevents other species from feeding and they can die from malnutrition. While they don’t necessarily play well with others, there are fish out there than can more than hold their own against the red tail shark.

What fish are compatible with the red tail shark?

Just because they look similar, don’t throw in a few rainbow sharks for good measure, that is just a disaster waiting to happen. Avoid other sharks if possible and other brightly colored fish that will attract the attention (or perhaps jealousy) of the bicolored red tail shark.

Bottom dwellers and peaceful fish should also be avoided because they are usually the ones who give in to excessive bullying and chasing. When in doubt, just keep one of these aggressors in their own tank.


Breeding is important for a fish on the endangered species list. Breeding in the aquarium trade has probably helped put them back on the map. The redtail shark is a mystery as we still don’t know too much about their breeding habits. Not many people attempt their breeding at home.

What we do know is that when the females are in heat, this is when you can more visibly see their rounded and plump abdomens. However, don’t eagerly go out and find her a mate just yet because these fish can’t stand the sight of each other (in pairs).

To save them from extinction (even though they aren’t found in the wild) commercial facilities have taken it upon themselves to breed this species. Hormones are introduced into their habitat at these facilities which triggers mating. It really doesn’t sound like something you can do at home, unless you somehow have the means of procuring the hormones.

When the female does become pregnant, it looks for darker and rocky areas to lay her eggs. In the wild, this would be inside caves. The redtail shark babies emerge in 40-60 hours and they come out silver in color. At about four days you will see the babies swimming about freely. Much like some salmon species, the redtail shark babies will change in color as they mature. They will soon evolve from silver to a silvery brown and eventually completely black.

Their iconic red tails emerge at about 10 weeks. The babies require small crustaceans or works (live food) at this stage to grow and develop well into maturity.


Red tail sharks are beautiful and rare (extinct in the wild) but they aren’t the easiest to get along with in the tank. If you already have a tank and are looking to add one of these beauties, you may need to reconsider. They are easy to care for just from an owner’s standpoint, but they can cause a lot of beginners headaches with their aggression.

Not only are they territorial, they need quite a lot of space. If you have the extra space, a lot of what makes them har to look after can be curbed with a larger tank, more substrate and proper tank mates. If you have everything down correctly, red tail sharks can make amazing pets. They are always busy, always entertaining and not to mention very coveted in the fishkeeping world and incredibly beautiful.

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