Redtail Catfish Care: Tank Mates, Diet, & Size

The Redtail Catfish is a truly monstrous fish. It’s a rare keeper that has the time, resources, and space to take care of them properly. I don’t recommend keeping one in a home aquarium and you’ll see why in just a moment.

So, let’s dive into the ins and outs of caring for one of these monsters, and convince you to not bring one home.

redtail catfish

Redtail Catfish Quick Care Sheet

  • Common Name: Redtail Catfish
  • Alternate Common Name(s): Cajaro, Pirarara
  • Latin Name: Phractocephalus hemioliopterus
  • Care Level: Advanced, Not Really Suited for Home Aquariums
  • Tank Size: 2,500+ Gallons
  • Size: 4’6” on average
  • Diet: Carnivorous
  • Behavior: Opportunistic Ambush Predator 
  • Lifespan: ~15 Years
  • Reproduction Type:  Egg Scattering, Nearly Impossible at Home
  • Water Temperature: 68-79°F (20-26°C)
  • pH: 6.0-7.0
  • Water Hardness: 3 – 12 dGH

Origins of the Redtail Catfish

The Redtail Catfish hails from South America, where it lives in deep rivers and lakes. They’re present in all of the major rivers in the region, including the Amazon, Essequibo, and Orinoco. 

There are also invasive populations spread across the world, from Thailand to the United States. These problems have been created by aquarists releasing them into the wild when they get too long.

As a matter of taxonomy, these are very interesting fish. They’re the only remaining species in the genus Phractocephalus, but the genus shows up in the fossil record going back 13.5 million years. Two species have been found thus far as fossils.

These ambush predators reach truly massive size. Some examples have reached over 180lbs at a length of 5’11”. More commonly they’ll be about 4’-4’6” when fully grown, which is still massive for a home aquarium.

If you impulse-bought one of these fish thinking they’re cool, and you’re not able to create a pond or aquarium in the >2000 gallon range, I recommend going down to our section on rehoming them immediately.

These fish grow very quickly. I’ve seen examples that have grown over an inch per week while juveniles. 

They’ll eat anything they can fit in their mouths, and they’ll do it constantly if given the opportunity. I’ve seen what happens when someone mistakenly sticks one in a community tank, and it’s not pretty.

They can be stocked with other monsters, but you still need to be careful. Even if you have the space, they’ll outgrow their tankmates and possibly have them for lunch. You can avoid that by raising the other fish separately, and only adding them when they’re big enough to not fit in the Redtail’s mouth.

The Redtail Catfish has a voracious appetite. Feeding them as they get larger can get expensive. Monster keepers are a different breed of aquarist, but looking through the various food items that Redtails eat is eye-opening.

Entire fish filets. Half a bag of jumbo shrimp. Whole crabs. Handfuls of pellets.

And that’s before they reach full size. Feeding monster fish is very expensive and at full size, you may be out a few hundred dollars just feeding the monster.

Then you get to worry about the utility bills that come with a tank or pond that’s over 2500 gallons.

On top of the sheer amount of space and food required, Redtail Catfish are sensitive to water quality. They require exceptionally clean water. Keeping these fish isn’t just a matter of digging a deep enough pond, you also have to have the experience to cycle and run a balanced system.

Did I mention they’re sloppy eaters as well?

Here’s the thing: the bare minimum requirements to keep a Redtail Catfish are immense. You need all of the following if you really think you’re up to the challenge:

  • Enormous Tank or Pond- 2500 gallons will house one Redtail Catfish. Most people already think a 125-gallon tank is a bit large, a 2500 gallon tank is bigger than most cars. The tank will have to be a custom, adding to the costs.
  • Great Filtration- That huge volume of water also needs to be clean, soft, and cycled. A tank for an RTC is often beyond “normal” aquarium gear. Pool equipment is going to be required to keep the water clean.
  • Food Budget- It costs more to feed a full-grown Redtail once than you’ll spend on most tanks in a year. I’m dead serious about needing a few hundred dollars extra each month just for feeding. Hyperbole is unnecessary when we’re talking about the RTC.
  • Utility Budget- The tank is going to cost more than having a pool each month, and you have to keep all of the equipment going year-round. Remember the tank needs to be at tropical temperatures. Oh, and you’ll be doing water changes on a weekly basis.

These fish are best kept by professionals. Even if you can meet the above requirements their care in captivity can be problematic.

The following information is not an endorsement to keep an RTC yourself. 

However, if we can’t convince you not to keep one then it’s best to give you the basic information to keep them healthy.

Redtail Catfish vs. Redtail Shark

These two fish sometimes get mixed up due to their similar names. Add in the fact that most “sharks” are catfish of some sort and you have a perfect storm of confusion.

Redtail Sharks are a Barb. They’re awesome little fish that are most at home in most semi-aggressive community tanks and a staple in the aquarium trade. They hit about 6” and need a 40 gallon or larger tank.

Redtail Sharks have a red tail and black body, along with the distinctive Barb profile. They have small barbels like all fish in their family.

The Redtail Catfish has a distinct catfish form. They have a dark body and white belly to go with their red tail. The long whiskers just confirm their heritage even to the casual observer.

While very distinct fish in every aspect you’ll occasionally see them conflated online. Seeing Redtail Sharks on blog articles about Redtail Catfish isn’t uncommon, so make sure you know the difference!

Ideal Tank Setup

Redtail Catfish are often kept in ponds instead of tanks. Ponds tend to be easier, and cheaper, to manage than aquaria at this size. The insulation from the ground saves a lot on heating bills alone, especially if the pond is indoors.

Specific equipment advice is useless at this size. 

There are no mass-produced tanks that size, you’ll have to work with a professional. They’ll know best what filters, heaters, and other pieces of equipment are going to be required. If you’re going it alone, you should look into pool equipment instead of aquarium stuff.

Tank Size

2500 gallons for a single Redtail Catfish. 

That’s not a typo, we’re talking two thousand, five hundred gallons of water.

That’s a 12’x6’x4’ tank. You can see an example of a custom here, just to give you an idea of what kind of space the fish is going to take.

The tank can’t be long and skinny, these fish need plenty of ground area to cover since they’re bottom dwellers.

Just finding someone to build the tank can be a chore, but most areas have at least one custom aquarium company around. Not everyone will take on the job, but they can point you in the right direction of folks who do larger customs.

If you can’t find a specialist, you can use an above-ground pool if it has enough capacity. This is going to be a temporary solution. Redtail Catfish are enormously strong and like to throw their weight around. 

A full-grown specimen can easily destroy the majority of above-ground pools

Location of Your Tank/Pond

Most monster fish end up in basements or garages. Both are a good idea, especially if they have access to the home’s heating system. Any garage where the tank is placed should be insulated to avoid heat loss.

You’ll also need to moisture-proof the room or run a dehumidifier. A tank of appropriate size will leave the room with very high humidity due to evaporation, which can wreak havoc on walls and anything unfortunate enough to rust in the room.

Indoors can be a pain, but it actually saves a lot on heating bills. If you keep the ambient temperature in your home at 72°F you’re in the right range and the tank will stay at room temperature.

Outdoor ponds may not need a heater if your local temperature stays over 68°F or so year-round. Otherwise, you need something to keep the temperature high.

Tank Decor

Redtail Catfish will eat anything that fits in their mouth. That includes rocks, driftwood, and plants.

That means your only real options are things like boulders or logs of driftwood. You can use them to build a decent aquascape for a biotope.

Anything else is pretty much toast if it’s in the tank with one of these fish.

Substrate

Since they’ll chow gravel or rocks, you really only have two options.

The first is just to leave the tank bare. This is the best route for most keepers unless you’re setting up a dedicated, and enormous, Amazon Biotope. RTC are sloppy eaters and a bare bottom prevents food debris from getting caught.

You can also use sand. You’ll be looking at 1-2 tons of sand to give a decent substrate for a 2500 gallon tank, not exactly something you can pick up at the local hardware store.

Tank Hood

Redtail Catfish are lively fish, and they have a bad habit of jumping out of the tank.

On a plus note, these fish lose the sharpness of their fin rays by the time they’ve hit 12” long. So at least you won’t get cut if you have to put the fish back into the tank.

On the downside… they’re strong enough to break most hoods. There are reports of them shattering glass and polycarbonate hoods, breaking pool covers, and other bits of mischief.

I recommend deferring to the specialists on this one. You need a hood for the tank or pool, but every situation is going to require a different solution.

Water Treatment and Changes

So, you have your 2500 gallon or larger tank and you’re ready to get it conditioned and ready.

Hold on for a second. These sloppy eaters are going to require a 30% water change most weeks.

That’s 750 gallons for a tank of the minimum size. Each week. That’s not a small amount of effort required, and working with tanks that large is different than working in “big” tanks like 125-gallon aquariums.

You’ll also need to treat that 750 gallons of water. You’ll be buying water de-chlorinator in bulk to keep up.

Specialized Care

The RTC is like a case study that shows what you don’t want in a pet fish. Even if you have all of the tank requirements sorted, you’re still in for a rough ride.

The three biggest factors left after you’ve got that 2500 gallons or more of clean water are the following.

Feeding Time

Redtail Catfish can, and will, eat just about anything. You’ll have to get creative as the fish gets larger, but most keepers end up feeding whole filets of fish and large chunks of vegetables.

As a juvenile, you’ll want to feed them something meaty like bloodworms or beef hearts every two days. You can avoid overfeeding by watching the fish’s belly, a full catfish looks pregnant and a hungry one has a flat stomach.

That trend will keep up for the duration of their lives.

Some are picky eaters and may begin to refuse food if they’ve eaten the same thing too often.

You didn’t really think that any part of keeping these fish would be easy, did you?

Most experienced keepers recommend feeding adults until full whenever their belly is flattened out. Feeding two or three times a week is common, but some specimens only seem to need to eat once a week.

Suitable foods, in case you run into a picky eater, include mussels, beef heart, blood worms, whole shrimp, whole crayfish, chicken, worms, and squid among others. The trick is to mix it in with some veggies to help the fish get full without too many calories.

Did I mention they’re prone to obesity?

Feeding an adult Redtail Catfish will require a lot of experimentation, but you should be able to find the right mixtures over time.

Diseases

Redtail Catfish aren’t immune to diseases.

Indeed, they seem to be quite vulnerable to the majority of ailments that hit fish. Clean water is of the utmost importance, but sometimes the fish will end up sick anyway.

You’ll now be treating 2500 gallons or more of water with medicine. A quarantine tank for a fully grown RTC is unrealistic for most keepers, but it should still be in the 1500 gallon range. And you’ll probably need three people to move the fish between the tanks.

A sick Redtail Catfish is an expensive problem, you’ll need to buy medicine by the gallon.

There’s not much you can do except to keep common aquarium medications on hand in sufficient quantities and keep the water quality as high as possible. Keeping the fish alone will also reduce the risk of infections or parasites.

Stunting

Most Redtail Catfish will die in subpar conditions.

The fact that they were sold as only reaching 12” for years is one of the more terrible things to come out of the aquarium trade.

Then you have the occasional person who will try to stunt their growth. This can be done intentionally or just through ignorance of fish husbandry. Some folks have been repeatedly told that fish “grow to their tank.”

Stunting a fish causes painful deformities and other problems in fish. Redtail catfish are no exception, they just require an enormous tank to not suffer from the effects.

These fish need room to grow properly.

I recommend not bothering with a smaller tank once they hit 12” or so. At that point, they should be placed in their final home to prevent the deformity caused by stunting.

Suitable Tankmates

If you actually have a tank in the 3000-gallon range or larger, you may be able to keep other fish in with your Redtail. Careful selection for size is the key, Redtail Catfish aren’t shy about showing you the error of your ways by making them disappear.

You’re best off with other large fish from the same region. Some of the following are suitable when fully grown:

  • Pacu
  • Giant Gourami
  • Stingray
  • Common Pleco
  • Arapaima

If a fish can fit in the RTC’s mouth, it’s toast. Their mouths open even wider than they appear at first glance.

I wouldn’t call Redtail Catfish aggressive. Hungry is a more accurate description of how they act. They’ll ignore most fish they can’t eat and aren’t prone to fighting over territory with other species.

It would seem natural to make a large, single-species enclosure for this fish but that’s not the best idea. They’re cannibalistic and don’t like other RTC in their space. You can sometimes raise them in a small group (Add 1,000 gallons per additional Redtail) if you get them at the same size.

Keeping multiple Redtails that get along has its own danger: they might breed. 

That sounds great until you realize they lay thousands of eggs at a time and every survivor is going to grow into a monster in its own right.

Keeping a single specimen is your best bet, but people have kept them with other fish in the past. It’s just a matter of how many fish get eaten before you figure out the right size.

Breeding Redtail Catfish

Do you have 25,000+ gallons of tank available, unlimited time to experiment, and the ability to acquire specialized fish hormones?

Well, you’re still on your own. There are rumors of these fish being bred in Southeast Asia through hormone manipulation, but no concrete proof.

They may just breed if you have more than one in a tank. That’s… a monumental disaster for most people unless you’re willing to just cull all of the babies immediately.

Simply put: there’s no publicly available information on how to breed these fish and you need six figures worth of tanks and ponds to do it right.

You need a commercial scale setup to even contemplate breeding them on purpose.

Resources for Rehoming Redtail Catfish

I hope you read this guide before you pulled the trigger on buying an RTC, but a lot of times people don’t know what they’re in for.

You should work on rehoming your fish immediately if you can’t provide the care described above.

I’ve seen keepers insist they’ll be able to sell their large RTC. They’re inevitably wrong, the truth is that these fish are so resource-intensive that few people want them. Fortunately, it’s easier than ever to find the few folks who do want an enormous catfish.

I suggest starting by searching for a fish rescue in your area. Depending on where you live, there may or may not be someone with space available.

If no rescue is able to take your Redtail Catfish in, I suggest calling any aquarium within driving distance, especially if they have Amazon displays. The sad truth is that most aquariums with the space and right exhibits… probably already have their fill of RTC.

After you’ve exhausted local options, I’d try online. Social media can be a good place and connect you with someone local. The most popular group I’ve seen is Ohio Fish Rescue, they do some amazing work and their page is a good resource to try and find someone local.

You may also want to try the old Monster Fish Keeper forums, which is a discussion board for hobbyists who keep large fish. The problem there is that a juvenile Redtail is about $25 and the majority of people who want one… have one.

Still, they may be able to point you to someone else.

If this sounds like a long, complicated process… you’re right. The truth is that I’ve never even seen a Redtail Catfish in a trustworthy fish store, and those that do lie about their size. It’s led to a lot of these fish ending up in bad situations.

If you can’t find anyone to take it, you may need to call your local Fish and Game Department. They should have an idea of how to find a place for the fish if they can’t do anything directly.

At the very worst they’ll euthanize it humanely. That’s not a procedure most people are able to undertake with a 100lb+ fish.

The best way to avoid this mess? Don’t buy a Redtail Catfish in the first place.

They’re easier to rehome when smaller but they grow rapidly. You need to act immediately if you have one that you won’t be able to care for, once they get over 12” the chances of finding a home go way, way down.

Do not release a Redtail Catfish into the wild. They’ve established invasive breeding populations in a few places, and they’re dangerous to any native wildlife due to their voracious appetite.

It’s never acceptable to release an aquarium fish in local waters, but doing it with an RTC is bordering on criminal negligence.

Beautiful Monsters

The Redtail Catfish is beautiful but too much of a monster for home keepers. We advise against keeping one, the above information shows just how unprepared most keepers are. Monstrously large, extremely strong, and oddly beautiful, the Redtail Catfish is best enjoyed in pictures and public aquariums.