Carnivorous freshwater aquarium fish are both sought-after and avoided in the fishkeeping hobby.
The aquarists who want them in their freshwater tanks are mostly fascinated by their predatory instincts and how their behavior has so much more intent and premeditation than peaceful fish.
Less experienced fishkeepers tend to avoid getting freshwater fish that are carnivorous because they have a preconceived notion that these fish are hard to feed and care for.
This is the common misconception that gives carnivorous fish their reputation as difficult pet fish: carnivorous fish = predatory fish = aggressive fish.
Most carnivorous freshwater fish have predatory instincts, but that doesn’t mean that they are all aggressive and/or territorial. There are some gentle-giants and some speedy & stealthy species among freshwater carnivores.
This article will walk you through everything you need to know about feeding and taking care of your meat-eating freshwater aquarium fish!
Carnivorous freshwater fish can be aggressive when faced with two main circumstances:
- Predatory instincts
If your carnivorous pet fish gets accustomed to a tank, and you introduce new fish that are small enough to be eaten in a mouthful, it’s only natural for a predatory carnivore to feast on its new tank mate.
But you’ll be surprised to find out that some carnivorous freshwater tank fish can be skittish and shy at first, even if they could easily eat the fish with which they share a tank.
- Territoriality
A territorial carnivorous fish will be aggressive if you keep it in a tank that’s not big enough.
There should be enough room in the tank to allow the territorial fish to set some boundaries for its territory while still leaving room for its tank mates to go about their business.
Some carnivorous freshwater tank fish species have their predatory instincts on high alert and display signs of territoriality at the same time. These are the type of pet fish that an aquarist should keep alone in a tank or as a single-species group.
Here are three carnivorous freshwater fish that you should definitely not keep in a community tank:
Red-bellied piranha
Piranhas are razor-toothed carnivorous freshwater fish that are native to the rivers and lakes of South America. They are infamous for their ferocity, but their aggressive behavior isn’t as intense as it’s hyped up to be.
In reality, red-bellied piranhas are not the apex predators most fishkeepers see them as. They are only ferocious when swimming in a shoal.
In the wild, a red-bellied piranhas’ diet will consist mainly of crustaceans, insects, worms, and fish.
They are best kept as a single-species group in a tank, as they are both territorial and predatory.
Arowana
The Asian Arowana can grow up to 36 inches in length, although most individuals will grow to an average size of 24 inches. Their sheer size makes it hard for them to share a tank, as they can make a meal out of most freshwater aquarium fish.
Arowanas are strong swimmers, making their predatory and territorial behaviors incompatible with community tanks.
This meat-eating freshwater fish will need a 250-gallon planted tank to thrive, and feeding it anything other than live food can be quite challenging. Arowanas need a diet of meaty food, including shrimp, crickets, and feeder fish.
Pufferfish
Pufferfish are feisty freshwater fish that hit all the checkmarks off the community tank incompatibility chart. They’re aggressive, predatory, and territorial.
They will eat fish smaller than themselves, they will harass and nip at similarly sized fish, and can pose a hazard for other carnivores in a tank, as they have poisonous spikes. So, they’re dangerous even when they’re the ones getting bullied!
In the wild, they feast on shellfish, crustaceans, snails, and small fish.
In the wild, predatory carnivorous fish feed on smaller fish. But in captivity, while being fed regularly and having enough room in a tank, typical predators will pretty much ignore smaller tank mates.
Some opportunistic carnivorous freshwater species will try to eat smaller fish on occasion. These species include Archerfish, Angelfish, Spiny Eels, African Butterfly fish, and some killifish species.
The misconception that carnivorous fish need to be fed live food exclusively will often deter fishkeepers from including predators in their community tanks.
The truth of the matter is that while carnivores thrive on a meaty diet, they can actually develop health issues from being offered feeder fish on a regular basis.
Predatory freshwater fish are rarely aggressive in the way that territorial carnivores can be. They display a variety of social behaviors, but most tend to be peaceful when kept in a heavily planted tank, with plenty of floating plants for them to prowl through.
The diet of carnivorous fish in captivity is one of the aspects that can sound intimidating to some aquarists. In reality, most carnivores will do best when offered a varied diet, which includes live food, frozen food, and enriched store-bought pellets/flakes designed for freshwater tank fish that are carnivorous.
What, and how do you feed carnivorous fish? Let’s find out!
Feeder fish – yes or no?
Although people outside of the fishkeeping hobby consider feeder fish a standard practice when keeping a carnivorous fish in captivity, this is definitely not the case.
Feeder fish are quite a controversial topic. Putting aside the ethical dilemma of introducing live fish into an aquarium so they can be served as a meal, feeder fish can actually be a harmful component in a carnivore’s diet.
Here are the two main reasons why including feeder fish in the diet of a carnivorous freshwater fish in your aquarium can harmful:
1) Thiaminase
The most common feeder fish species fishkeepers go for are Rosy Red Minnows, Goldfish, and other members of the Cyprinidae family.
The issue with this is that by feeding carnivores using fish from this family, they include a large amount of fat in their diet and thiaminase.
Thiaminase is an enzyme that destroys thiamine, which is vitamin B1. By having too much thiaminase in their diet, carnivorous fish become vulnerable to a myriad of health problems (abdominal swelling, skin hemorrhages, nervous behavior, loss of swimming abilities, and poor resilience to diseases in general).
Feeding fatty feeder fish to predatory carnivorous fish can cause premature deaths, mostly due to abnormal fat deposits on their internal organs.
2) Parasites
Feeder fish are bred and raised with the sole purpose of serving as live prey for carnivorous fish. To sell them at a low-price level, they’re often kept in less-than-ideal conditions.
They can carry parasites, which means that using feeder fish to feed your carnivorous pet fish will invariably expose them to a higher risk of developing parasitic infections.
The answer to the initial question is “no” so far.
Can you safely feed carnivorous fish using feeder fish?
Yes! With the assumption that you can take on the task of breeding them yourself.
The common Molly, or Mosquitofish, are thiaminase-free feeder fish that are great low-fat alternatives to commercially-bred feeder fish.
You can also use them to add extra vitamins and nutrients to the diet of your carnivorous pet fish, by feeding the feeder fish vitamin-packed fish food while raising them.
- Other live food
A single freshwater fish that is carnivorous can devour a substantial number of live fish in a short period of time. This means that breeding and raising feeder fish yourself can quickly become an expensive and impractical option.
There are plenty of other live food alternatives you can use to keep a predatory carnivores’ appetite satisfied. Invertebrates, such as earthworms, river shrimp, and various insects, are all awesome nutrition-rich live food options for carnivorous fish.
- Frozen food
Even with safer and less expensive live food alternatives, live food can be difficult to store and still push a fishkeeper’s budget beyond a comfortable limit.
There are plenty of reasons why aquarists that gain some experience with keeping carnivorous fish will often choose to wean them towards a diet that consists of mainly nonliving food.
With a bit of patience and by finding ways to stimulate your carnivore’s predatory instincts, you can get most carnivorous fish to eat frozen food.
You can feed carnivorous fish plenty of commercially sold fish species that don’t contain thiaminase.
Buying whole fish, rather than fillets, will help you save quite a bit of cash. You can chop up whole frozen fish into smaller bite-sized chunks (innards and all).
Some frozen fish you can find on the market that don’t contain thiaminase are:
- freshwater gamefish (fish from the Percidae family);
- Tilapia;
- Flounders;
- Cod;
- Pollack.
Variety is key
There’s not one single type of food that you should feed carnivorous freshwater fish in your aquarium.
Offering a variety of frozen food and live food will offer your freshwater carnivores the best of both worlds, nutritionally speaking.
Feed them a balanced combination of:
- vitamin-packed live food (which was previously fed high-quality flakes/pellets);
- shrimp, earthworms, insects;
- frozen thiaminase-free fish;
- and even flake/pellets designed for carnivorous fish.
This feeding routine will keep your predatory carnivorous pet fish interested and engaged.
A bored predator will prefer to go without food. Variety truly is key to feeding carnivorous fish!
How to get carnivorous freshwater fish in your tank to eat non-living food
Live food has the benefit of enticing a carnivorous fish’s predatory instincts, which makes the entire feeding process easier (and sometimes quite entertaining).
In order to wean a carnivorous fish onto nonliving food, you’ll need to use a more hands-on approach.
There are two tried and tested methods you can use:
- Hold (and wiggle) chunks of food using a pair of aquascaping tweezers. With a bit of luck, your predatory pet fish will follow its instincts and strike, swallowing the food whole.
- Throw chunks of food into a strong water flow – this might work better if you allow a carnivorous fish to get a bit hungry before attempting to feed it.
Carnivorous fish will quickly learn to associate your presence with being fed, so you’ll only need to use these methods for a short period of time. Predatory fish in captivity have proven themselves to be uniquely intelligent!
Whether or not you can find compatible tank mates for your carnivorous pet fish will depend on the size of the aquarium you’ll have them share.
A large enough tank will give the carnivorous fish plenty of room to swim and lurk while pretty much ignoring smaller fish. This is the best-case scenario!
If you want to introduce a carnivorous fish in a community tank, you’ll have to look into peaceful, or at most, semi-aggressive carnivores.
Semi-aggressive carnivorous fish will do well in community tanks if you pair them with fish that mostly occupy other parts of the tank than themselves. Their semi-aggressive nature is linked more to their territoriality than it is to their predatory instincts.
Some freshwater carnivores (such as piranhas) are simply not adaptable enough to try to play nice with peaceful fish species. They can see smaller fish as food and prey on them if they haven’t been introduced as juvenile fish at the same time.
Ironically enough, some predatory carnivorous fish will be quick to hunt but too skittish to fight. So, you can keep predators with similarly sized carnivores, as they will avoid each other’s presence.
Keep in mind that a generously-sized tank is a MUST!
Here is a list of some of the most common freshwater aquarium fish with a carnivorous diet:
Angelfish (Pterophyllum scalare)
While they have an omnivorous diet in the wild, Angelfish are mainly meat-eaters.
Their list of favorite food includes brine shrimp and mosquito larvae.
|
Angelfish (Pterophyllum scalare) |
|
| Care level | Medium |
| Size | 6 inches |
| Lifespan | 10 years |
| pH range | 6.8-7.8 |
| Temperature | 78-84°F |
| Temperament/Behavior | Semi-aggressive |
| Alternative names | Freshwater Angelfish |
- Angelfish Tank Mates
Angelfish are best kept with other angelfish or in a tank large enough to deter them from eating smaller tank mates.
|
Ideal Tank Mates |
Not Recommended |
| Corydoras Catfish | Tetras |
| Platies | Barbs |
| Dwarf Rainbow Fish | Guppies |
| Zebra Loaches | |
| Mollies |
Oscar fish (Astronotus ocellatus)
Oscars will eat an omnivorous diet in their natural habitat, but they are carnivores at heart.
They will eat brine shrimp, daphnia, and bloodworms, as well as flakes/pellets designed for cichlids.
|
Oscar fish (Astronotus ocellatus) |
|
| Care level | Medium |
| Size | 15 inches |
| Lifespan | 10 to 20 years |
| pH range | 6.0-7.5 |
| Temperature | 77-80°F |
| Temperament/Behavior | Aggressive |
- Oscar Fish Tank Mates
Keeping Oscars in a community tank puts smaller fish at risk of getting eaten.
They do well with similarly sized peaceful fish in a large-enough aquarium.
| Ideal Tank Mates |
Not Recommended |
| Catfish | All smaller fish species |
| Silver Dollar Fish | |
| Jack Dempsey Cichlid | |
| Blue Acaras | |
| Firemouth Cichlids |
Discus (Symphysodon)
Discus are a bit more high-maintenance than other carnivorous fish, as they have a strong preference for some particular water conditions.
They will eat crustaceans, amphipods, copepods, bloodworms, brine shrimp, mosquito larvae, and even chunks of beef heart.
|
Discus (Symphysodon) |
|
| Care level | Medium |
| Size | Up to 6 inches |
| Lifespan | 10 years |
| pH range | 6.0-7.0 |
| Temperature | 82-86°F |
| Temperament/Behavior | Peaceful |
- Discus Tank Mates
Discus are among the most peaceful carnivorous fish for a freshwater aquarium.
They can even get bullied and harassed when sharing a tank with aggressive fish species.
|
Ideal Tank Mates |
Not Recommended |
| Bristlenose Plecos | Barbs |
| Cardinal Tetras | A large school of Tetras |
| Sterbai Corys | Angelfish |
| Dwarf Cichlids | Clown Loaches |
| Emperor Tetras | German Blue Rams |
Killifish (Cyprinodontiformes Family)
Killifish (a family that includes over 700 species) prefer eating live food and are harder to wean onto nonliving food.
You can feed them brine shrimp, mosquito larvae, daphnia, white worms, black worms, and fruit flies.
|
Killifish (Cyprinodontiformes Family) |
|
| Care level | Medium |
| Size | 1 to 2 inches |
| Lifespan | 2 to 5 years |
| pH range | 6.6-7.2 |
| Temperature | 72-75°F |
| Temperament/Behavior | Peaceful / Aggressive only with other males |
- Killifish Tank Mates
Killifish are notorious for getting aggressive with other males, from their own species and other fish species their size.
Females, on the other hand, can peacefully share an aquarium with lots of popular community tank fish.
|
Ideal Tank Mates |
Not Recommended |
| Danios | Other male Killifish |
| Rainbow Fish | Similarly-sized males of other species |
| Tetras | |
| Smaller Catfish | |
| Dwarf Cichlids |
Jack Dempsey cichlid (Rocio octofasciata)
Jack Dempsey fish have a quick temper, which results in aggressive displays of territorial behavior.
They will eat smaller fish in a blink of an eye. Their diet typically includes crickets, snails, bloodworms, brine shrimp, and small feeder fish.
|
Jack Dempsey cichlid (Rocio octofasciata) |
|
| Care level | Easy |
| Size | Up to 12 inches |
| Lifespan | 8 to 10 years |
| pH range | 6.0-7.0 |
| Temperature | 72-86°F |
| Temperament/Behavior | Aggressive |
- Jack Dempsey Tank Mates
Jack Dempsey cichlids do best when sharing a large aquarium with similarly-sized semi-aggressive fish.
| Ideal Tank Mates |
Not Recommended |
| Oscars | Smaller peaceful fish |
| Kissing Gouramis | |
| Clown Loaches | |
| Firemouth Cichlids | |
| Rasboras |
Freshwater carnivorous fish are rarely the aggressive and high-maintenance pet fish that they’re considered to be. Some of the most common fish in the hobby are avid meat-eaters, while also being beginner-friendly.
It’s true that some carnivorous fish have some pretty specific care needs, but with a bit of research and patience, any aquarist can handle keeping a freshwater carnivore in captivity and having it thrive!
Recommended Reading:
- How To Tell If Angelfish Eggs Are Fertilized – Complete Breeding Guide
- How To Prevent Fish From Getting Stuck To Filter – All You Need To Know
