Aquarium catfish are a common sight in aquariums around America, but many beginner hobbyists misunderstand how these armored fish interact with others in a tank. Can aquarium catfish be aggressive, and what fish are they safe to pair with?
Most species of catfish are territorial but not highly aggressive. They can, however, be aggressive towards others of their own kind during breeding season. Catfish will attack slow-moving bottom dwellers and fish or invertebrates much smaller than themselves.
Catfish do well with most other tankmates, but they do have a very real mean streak that should give you pause before adding other bottom dwellers to your tank.
Read on, because I’m going to explain the temperament of catfish. I’m also going to share some of my personal experience with catfish to recommend some ideal tankmates for you.
Table of Contents
Can Catfish Be Aggressive in a Tank?
Catfish in a tank, just as in the wild, can be territorial. The reason most beginner aquarists–indeed, even online sources–denote catfish as peaceful is because they are not big enough to cause serious harm to other fish. Make no mistake, some catfish, especially ones that grow 6 inches or bigger, will attack smaller fish or slow moving fish that tend to sit on the bottom.
The general rule with catfish is not to keep them with any other fish that can fit in their mouth. In other words, it’s not sensible to put a larger catfish in with smaller fish that they may harm.
The red tailed catfish, for example, which grows to about 3-4 feet and is highly aggressive, is not a suitable tankmate for smaller fish like mollies, platies, or guppies.
Often, catfish tend to be aggressive for various different reasons, which I’ve mentioned below.
Mating Rights
When breeding season rolls around, male catfish will be particularly aggressive towards each other. Depending on the species, that aggression can spread to other fish, especially those that linger around the bottom. While it’s not unusual to see fighting over mating, it can be dangerous for other smaller fish.
Keep your catfish in groups of at least 4-6 to spread the aggression; doing so can help smaller catfish who would otherwise be picked on, as well as females who take on the brunt of the aggression.
Food
Catfish can be aggressive over food. In a tank environment, it’s not usually something you need to worry about, as long as you don’t have other species of smaller fish or invertebrates feeding on the bottom.
Cory catfish, for example, feed on the bottom and may chase each other around to secure feeding rights, but as long as you have the appropriate group size, catfish aggression shouldn’t disrupt your feeding schedule.
Monitor your tank when you feed to make sure that all inhabitants are getting food as needed; you may find that you need to feed more in a smaller tank or a tank with lots of fish to make sure everyone gets enough to eat.
Territory
Territorial disputes are the most common type of aggression exhibited by catfish. In a tank, catfish establish a space for their home and will fight to defend it. Again, this sort of aggression is expected and normal among catfish and shouldn’t pose an issue.
Be careful if you have catfish that are much different in size; the larger may do some serious harm to the smaller catfish. In general, you can lessen the likelihood of territorial disputes if you increase your tank size.
Group Order
Most species of catfish do better in a small group of 4-6 so that no one member is singled out for bullying. Catfish do not school as other fish do, but they are usually found living near other catfish. As such, it’s a balancing act of community and personal space.
Catfish may fight over their ranking in the hierarchy. The largest of the catfish will usually show aggression by fighting for breeding rights, territory, and food, establishing themselves as the dominant catfish.
Given enough tank space and plentiful hiding spaces for lower-ranking catfish to retreat and call home, group aggression isn’t a problem among most catfish species.
Which Catfish Are the Most Passive?
Most species of catfish exhibit territorial behavior to some degree, but some are small enough or shy enough that they can be included in most community tanks with little issue. Some of these passive catfish include:
Bristlenose Pleco
| Temperament | Peaceful |
| Minimum Tank Size | 30 gallons |
| Fish Size Range | 3-5 inches |
| pH | 5.7-7.8 |
| Diet | Herbivore |
| Care Level | Easy |
| Temperature | 73-81 F |
Bristlenose plecos are great catfish for any community tank. They’re pretty, keep to themselves, and are extremely easy to care for. I’ve owned Bristlenose plecos for years and found them to be great pets, never bothering any other fish–even other plecos–on the floor.
Corydoras
| Temperament | Peaceful |
| Minimum Tank Size | 20 gallons |
| Fish Size Range | 1-4 inches |
| pH | 5.5-7.0 |
| Diet | Omnivore |
| Care Level | Easy |
| Temperature | 70-78 F |
I’ve kept cories in my tanks for as long as I’ve been an aquarium hobbyist. They’re extremely chill, adaptable to a range of tank conditions, and–might I say–adorable to boot. With lots of different types of cories, these are the most peaceful freshwater catfish out there and work perfectly in any community tank.
Otocinclus
| Temperament | Peaceful |
| Minimum Tank Size | 10 gallons |
| Fish Size Range | 1-2 inches |
| pH | 6.0-7.5 |
| Diet | Algae-based |
| Care Level | Easy |
| Temperature | 72-78 F |
Otocinclus are the algae-gobbling, peaceful catfish that everyone adores. Their small size makes them adaptable to any type of tank environment and amenable to almost any tankmate. Be aware that the tank parameters to keep one of these catfish are a little tighter, specifically the temperature and pH, although the Otocinclus itself is very easy to care for.
Pictus Catfish
Image source under CC BY-SA 2.0 DEED
| Temperament | Non-territorial |
| Minimum Tank Size | 50+ gallons |
| Fish Size Range | Up to 5 inches |
| pH | 7.0-7.5 |
| Diet | Ominvore |
| Care Level | Moderate |
| Temperature | 74-78 F |
Pictus add a splash of silver to the bottom of any tank, and their unique look makes them a great pet. Just be mindful that pictus aren’t aggressive, but they will chomp on anything that fits into their mouth. They also have fairly strict tank parameter requirements. Even so, their personality and relatively peaceful nature make them a great pick.
Bumblebee Catfish
| Temperament | Very shy |
| Minimum Tank Size | 20 gallons |
| Fish Size Range | 1-2 inches |
| pH | 6.5-7.5 |
| Diet | Ominvore |
| Care Level | Easy |
| Temperature | 70-77 |
Bumblebees are adorable, shy, and fairly easy to care for. They’re a great entry fish, and a little exotic if you’re feeling adventurous stocking your tank. Their steady small size makes them appropriate for smaller tanks, letting you ease into tank maintenance. Just be mindful that sudden temperature shifts can cause illness; that’s true of any fish, but the bumblebee catfish is particularly susceptible to quick changes in temperature.
Glass Catfish
| Temperament | Peaceful |
| Minimum Tank Size | 30 gallons |
| Fish Size Range | Up to 5 inches |
| pH | Slightly acidic (around 6.5) |
| Diet | Ominvore |
| Care Level | Moderate |
| Temperature | 75-80 F |
Glass catfish are quirky, yet cute. Their transparant bodies and short whiskers make them an interesting pet and a good foray into your first catfish. They do have fairly strict care requirements so keep that in mind before you purchase one; nevertheless, these catfish won’t be bothering any of your other fish.
Clown Pleco
| Temperament | Peaceful |
| Minimum Tank Size | 30 gallons |
| Fish Size Range | 3.5-4 inches |
| pH | 6.0-8.0 |
| Diet | Ominvore, wood-eater |
| Care Level | Easy |
| Temperature | 73-82 F |
I love my clown plecos. They’re constantly busy around the tank rasping on wood and eating algae. They also make for a great splash of color. The best part is that these plecos are hardy and can live for 10-12 years, making them a great long-term pet for your aquarium. Completely relaxed, peaceful, and very easy to care for, the clown pleco is a must-have.
What Tankmates Are Compatible with Catfish?
Any fish that swims in the middle or top of the tank is safe with the catfish mentioned in the list above. As mentioned, the general rule of thumb is to avoid small fish that the catfish could eat or slow-moving bottom dwellers that cannot escape.
Some compatible tankmates for common peaceful aquarium catfish include the following:
Mollies
Black Molly by Marrabbio under CC BY-SA 3.0
| Temperament | Peaceful |
| Minimum Tank Size | 10 gallons |
| Fish Size Range | 3.5-4.5 inches |
| pH | 7.5-8.5 |
| Diet | Ominvore |
| Care Level | Easy |
| Temperature | 75-80 F |
Mollies come in a wide range of colors and sizes, making them a great fish to spice up your tank. They’re hard, peaceful, and very enjoyable to watch. They’re rarely ever aggressive, except in crowded or unhealthy tank conditions. Every tank I’ve kept mollies in has been a success; they’re just that versatile.
Guppies
| Temperament | Peaceful |
| Minimum Tank Size | 20 gallons |
| Fish Size Range | 0.5-2.5 inches |
| pH | 6.8-7.8 |
| Diet | Ominvore |
| Care Level | Easy |
| Temperature | 73-82 F |
If you ask an aquarist to name a peaceful fish, you’ll likely be met with several answers of “guppy.” That’s because the guppy one of the most common peaceful fish out there. I love guppies in my community tanks because they fit the bill perfectly. They’re small, entertaining and the males feature a range of dazzling colors. Just be mindful that you need a large-enough group to spread aggression out (the males tend to harass the females). Guppies are prolific breeders, but just about everything (including your catfish) will gobble up the liveborn fish fry. Keep your guppies separate if you’re planning to breed them.
Platies
Image by Marrabbio2 under CC BY-SA 3.0
| Temperament | Peaceful |
| Minimum Tank Size | 10 gallons |
| Fish Size Range | Up to 2.5 inches |
| pH | 6.8-8.0 |
| Diet | Ominvore |
| Care Level | Easy |
| Temperature | 70-77 F |
Low-maintenance, hardy, and docie, the platy is the perfect blend of color and personality. If you’re setting up a community tank, you really can’t go wrong with these fish.
Neon Tetras
Image by H. Krisp under CC BY 3.0
| Temperament | Peaceful |
| Minimum Tank Size | 10 gallons |
| Fish Size Range | 1-1.5 inches |
| pH | 6.0-7.0 |
| Diet | Ominvore |
| Care Level | Easy |
| Temperature | 70-81 F |
Neon tetras are a great schooling fish with a bright blue stripe down their bodies. They school well, add a splash of color, and are very easy to care for. They keep to themselves and can live up to 8 years, making them a good long-term fish for a community tank.
Harlequin Rasboras
Image by Stefan Maurer under CC BY-SA 2.0
| Temperament | Peaceful |
| Minimum Tank Size | 10 gallons |
| Fish Size Range | 1.5-2 inches |
| pH | 6.0-7.8 |
| Diet | Ominvore |
| Care Level | Easy |
| Temperature | 72-81 F |
Rasboras are one of my favorite ditherfish in the world. They fill space wonderfully and make a tank feel more alive. Include enough to school and provide a varied diet, and these fish practically take care of themselves. They’re non-aggressive and go great with any passive species of catfish.
Tiger Barbs
| Temperament | Semi-aggressive |
| Minimum Tank Size | 20+ gallons |
| Fish Size Range | 2-3 inches |
| pH | 6.0-8.0 |
| Diet | Ominvore |
| Care Level | Easy to Moderate |
| Temperature | Around 75 F |
Tiger barbs are beautiful with their orange and black stripes. They do have a bit of a reputation for being fin-nippers, so it’s important to provide your catfish with plenty of places to hide and include a large-enough school of barbs to spread the aggression around and reduce stress-related aggression.
I love tiger barbs and have kept them successfully with cories, bristlenose plecos, clown plecos, wood plecos, and pictus catfish without any problem.
A Note on Semiaggressive Tankmates
Again, it’s important to mention that tank size plays an important role in aggressive behavior exhibited by catfish. They will be more nippy towards their neighbors if they feel as though other fish are encroaching on their space all the time.
Some semi-aggressive species of fish can be kept with catfish without problems, as long as they have plenty of places to hide and seclude themselves.
Betta fish, for example, are ok to keep with the above-mentioned catfish species. The catfish will not bother the Betta fish, and the Betta is not big enough or aggressive enough to pose a hazard to the catfish.
Angelfish are another good example. Whereas other, smaller species of middle-dwelling fish would be constantly bullied by an angelfish, catfish can comfortably manage with these semi-aggressive tankmates.
What Tankmates Are Not Compatible with Catfish?
Of course, there are some tankmates that are not ideal to pair with catfish, usually because they pose a threat to the catfish, or the catfish poses a threat to them.
Crayfish
Some tankmates that are not compatible with catfish include other invertebrates like crayfish. Crayfish are aggressive creatures that dwell on the bottom of the tank and won’t hesitate to pinch other fish that venture too close.
Of course, for fish that swim quickly in the middle or top of the tank, this isn’t an issue. Catfish, who dwell on the bottom, are much more likely to be picked on, and a crayfish can give a nasty pinch when it wants to.
Cichlids
One middle-swimming fish that isn’t compatible with catfish is most species of cichlids. Cichlids tend to be highly aggressive and often serve as the centerpiece of a tank. They constantly fight with other fish over food, mating rights, and territory. It’s built into their nature, and larger cichlids can do a lot of harm, especially to smaller catfish like cories.
Shrimp
On the flipside of the coin, catfish can be the aggressors when it comes to smaller creatures like shrimp. Shrimp are just too small and too slow-moving to be safely put in a tank that has catfish, especially catfish that get to be upwards of 6 inches.
Nanofish
Smaller fish aren’t safe either. If a catfish can fit a fish in its mouth, then that fish isn’t compatible. This encompasses a broader categorization of fish called nanofish. These might include danios, kuhli loaches, and pygmy cories. These fish might be ok with smaller catfish, but any catfish that grows to an adult size of 5 inches or more poses a hazard to these fish.
Many fishkeepers do keep catfish with nanofish, and it is sustainable with the right setup. Just be aware that you undertake a risk of injury or death to your nanofish if you choose to pair the two.
Fish Fry
Lastly, any newly hatched fish are susceptible to catfish. They, along with almost every other fish in the tank, will eat fish fry and fish eggs.
This is particularly noteworthy for catfish because fry may linger near the bottom of plants or under decorations–the primary hiding places for catfish. Catfish may also be uniquely positioned to gobble up fish eggs that float down to the bottom of the tank undetected.
FAQs
Are Aggressive Catfish Good Pets?
Aggressive catfish can make great pets if you put them with the right tankmates and in an appropriately sized tank. Generally, you’ll need to pair them with similarly sized, similarly aggressive fish who can hold their own.
Will Catfish Attack Other Catfish?
Catfish will attack other catfish, either of their own species or different species. The primary reason is that they are occupying the same floor space. In a smaller tank, conflicts and injury are more likely between catfish.
Conclusion
Catfish can be territorial, but with most common aquarium species, they are not highly aggressive. Steer clear of slow moving bottom dwellers or tankmates that will pick on the catfish, and you’re sure to have a great selection of fish for your tank!
Be sure to read the helpful info above to see what tankmates I recommend for your catfish!
