Do fish kill each other?

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Fish owners know the joy that comes with having a tank. These creatures are so magnificent and are pretty much one of the best cold-blooded pets, if not the best you can have. Having a fish pet is so great as these creatures go about their own business without any hassles. Another outstanding characteristic is how they manage to recognize their owners, which is stunning. If you want a serene moment while spending time with your pet, getting a fish is the best bet.

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Despite these great qualities about fishes and their behaviors, there are times they do get piped up. You really don’t want to see an angry fish as it can throw a fit. While this particular behavior can be comical, it can also spell serious trouble if you have more than one fish in your tank, and one of them is the target of the angry one. Many times, fish owners have seen how this situation plays out and how they had to intervene to avoid severe damage from happening. This particular behavior has made fish owners ask if fishes can kill each other? The simple answer is yes. But there are many factors responsible for this shocking behavior, and we will talk about the most obvious below.

A fish will, in most cases, only attack another fish when they are of different species. Some fishes do not enjoy sharing space with other species and would attack until a separation is done. If nothing is done, the dominant or stronger species could kill the weaker one.

Another reason that could make a fish kill another is when they are territorial in nature. Territorial fishes do not care about their species and will attack their kind if they sense an invasion of their space. This behavior is typical of male Betta fishes who can fight until the weaker one is dominated and, if unfortunate, killed. So from all of these scenarios, it is obvious that fish can kill each other.

Do fish kill each other

Why Do Fish Attack Each Other? 

Fish in an aquarium can become aggressive and attack other fishes for several reasons. These are some of the reasons why they do so;


Aggressive fishes will attack and chase away other fishes as they do not like to share food, and this behavior can be worsened when there is no adequate supply of food.

Aggressive Fishes In The Same Tank. 

Aggressive fish will always attack other fish for dominance/superiority and also when they feel threatened. Several aggressive fish in an aquarium would result in a series of fights and attacks. To avoid this all fishes should be introduced to the tank at the same time. This will help each one find their comfort zone and drastically reduce confrontation.


A Fish could attack another due to it being territorial in nature. Territorial fishes can be very vicious to space encroachers. In several instances, territorial fishes take over corners of their tank and would attack any fish trying to enter its home. To prevent this situation, owners should always rearrange the tank whenever a new fish is to be introduced into the aquarium. This allows all the fish in the tank to find new comfortable territories and help reduce territorial attacks.

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How Do I Know If My Fish Are Fighting? 

Fishes can get touchy when playing by swimming and rubbing against each other, and this is usually not a situation to worry about. However, if this behavior continues for longer than several minutes and the impact becomes more aggressive, then it could be that your fishes are fighting.

Paying keen attention to your fishes will let you know if they are fighting or playing. The intensity of their collision and nipping can be an obvious indicator. If their strike is light, sporadic, and quiet, then they are probably playing. But if it’s loud and there are pieces of fins around, a fight is likely happening.

Territorial fish that try to protect their space in a tank should also be watched closely, as they could be very aggressive with fish of the same sex and species. These fishes could fight over mating rights and control of the females in the tank. Owners should always watch out for male species keenly as they are quick to start a fight because of their dominating and territorial behaviors.

If an aquarium owner comes back to the tank and wants to find out if there was a fight, physical evidence from the fishes’ bodies like scratches, missing scales, injuries on the body, and split fins are definite signs. If an aquarium owner comes back to find its fish changing their territory, this is a sure sign of a possible fight over territory, and the winner is in charge.

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Do Goldfish Fight And Kill Each Other? 

Goldfish are one of the best fishes to start with if you want to start a tank. They are known for their calm behavior and are pretty much one of the friendliest fish you could have in your tank; one of the reasons they are very popular. Many pet fishes are known for being a tad aggressive and territorial, but this is barely the case with a goldfish.

However, no matter how good a situation may be, there is always an exception, and this also applies to goldfishes. Some of these species can be a little crazy to start a fight, with some owners having experienced this on occasions.

Goldfishes on rare occasions could fight each other when they are competing over something like food. This will only happen, though, when food is scarce, a condition that you determine.

Another reason that could trigger fighting in goldfishes is on the rare occasion of one being aggressive. While Goldfish are generally gentle-natured, some could actually be aggressive and push against another goldfish. They could also chase the others and, in the worst scenario, nip at the others.

From the above cases, it is clear that Goldfishes can fight though it barely leads to any real injuries. This also means that Goldfish do not kill each other.

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Why Are My Fish Attacking One Fish? 

After setting up an aquarium with the required temperature, plants, and decorations, the next step to naturally take is to begin stacking different species. After doing this, owners may notice that fishes constantly attack one of their mates and regularly stop them from having food. This is referred to as fish bullying.

Firstly, before concluding that a fish is being bullied, you must first be sure that it is not a play fight mistaken for bullying. Sometimes, when males are about to mate with females, they could start a chase similar to an attack, which could be confused with bullying.

Another reason that could lead to a fish being attacked is if there is a lone species among a crowd of naturally aggressive species. The lone fish will continually be a target and will be subjected to a lot of stress. You can offset this imbalance by getting more of the solitary species if that will help or separate it from the crowd.

Finally, a small fish in the midst of bigger ones will no doubt be a target for the big guns. They will keep chasing it and prevent it from getting food, and this situation is only made worse when there is no hiding place for the fish.

Do Goldfish Eat Each Other When Dead?

Goldfishes are known for their gentle nature, making them one of the most popular pets for tank owners. They usually mind their business, do well alone, and do not necessarily need companions. In cases when their personal spaces are encroached by introducing a new goldfish or a different species, they are typically tolerant and do not mind sharing. These characteristics normally make tank owners believe that Goldfish can do nothing unusual, like eat their own.

While some owners have claimed that their Goldfish actually feast on themselves, many are skeptical of these claims, which is why we will be providing answers to this question. 

It is worthy of note that goldfish, except out of unexplainable circumstances, will never kill themselves for any reason. However, Goldfish can feast on their own kind when a fish is dead. With no real ability to decipher what death means, goldfish, like most fishes, see unresponsive and decomposing fishes as food and will feast on them even if it is their kind.

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Now that it is confirmed that goldfish can actually eat their dead kind, it is very important to know how to avoid this situation due to health concerns for the ones alive. The moment You notice a dead fish in the tank, you should quickly evacuate it so that others do not eat it and contract a potential health impediment from the dead fish if it died from strange circumstances. You can also call a vet to find out the circumstances of the fish’s death and, if anything is found, confirm if it is transferable or not.

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Why Do Fish Eat Other’s Fish Fins?

Fishes fight. This is one truth you should be ready for as a tank owner. With the rise of the Internet and information availability, most fish owners are aware of the possibility of fish fights happening. These have better prepared them and make them ask questions on how to stock for their tank. However, some aspiring owners may not know the importance of this process and end up stacking several wrong species of fishes together, which later cause problems that include fin nipping.

Fin nipping is a common problem and is mostly avoidable as fishes will only eat another fish fin if there is a wrong stacking choice. Fishes of different species may fight, a common characteristic with tiger barbs. Tiger Barbs will, on most occasions, attack other species of fishes and nip on their tails. This could lead to severe injuries and even death for the attacked fish, which is why it is essential to keep tiger barbs away from fishes that they see as easy pickings.

Another reason why a fish may eat on another fin is due to territory protection. These types of fishes do not care about species and will attack any perceived invader. You can help sort out this issue by getting a well-spaced tank with several hiding places to avoid this. It is best to get separate tanks if you can afford them.

Why Are My Fish Nipping At Each Other? 

Fish nipping is characterized by fishes biting off other fishes’ fins due to territorial or incompatibility reasons. This is a prevalent problem that many aquarium owners face. Below are some of the reasons for fish nipping.

Firstly, fish compatibility is crucial and an essential factor that must be considered when stocking your aquarium. For example, a tank with Neon Tetras that have a reputation for excessive nipping should not have a Betta fish or angelfish for company as these are naturally long-finned.

In an Aquarium where fish nipping is prevalent, it could be that a dominant fish is harassing another fish. Once this is noticed, it’s best to separate the dominant fish from the other tolerant ones.

Another cause of nipping could be underfeeding. If fishes are not adequately fed, then they may lash out and nip at each other for sustenance. An underfed fish can be easily spotted by taking note of apparent signs such as reduction in size and weight, constant digging into the tank substrate in search of food, and nipping if it is bigger. If any of these signs are observed, then you have to increase your fish’s daily feed.

Overpopulation could lead to nipping as too many fishes in a tank can result in aggression and fights. You can know if your fishes are being overcrowded or if your tank is too small by following the rule of one fish to two gallons of water to not overcrowd the tank.

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Another cause of nipping could be the proportion of males to females in the tank. To avoid attack or fin nipping, it’s essential that the female fish are proportionate to the males or at least close to prevent competition.

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Why Fish Keep Chasing The Other One? 

Fishes can chase each other for a lot of reasons and may not necessarily be due to aggression. They could be playing and enjoying themselves. However, it is essential to pay attention if your fish is being chased around and find out the cause. Here are some reasons a tank chase can occur


A male fish could chase a female fish during courting or mating, and the role can be reversed when the female is giving signals that it’s ready to mate. Also, if there are many males and few females in the tank, a bigger or stronger male could chase other fish in the act of dominance.


Not all fishes species are compatible, and this problem can be more obvious in a limited environment like an aquarium. Species like the Betta fish are prone to chasing other fishes around due to them being territorial in nature. So aquarium owners should consider this when pairing fish species in a tank.


This is very common in a tank filled with a lot of fishes. Aquarium owners who do not provide enough food will notice a lot of aggression, such as weaker fishes getting chased around. In such situations, owners should check for each species’ particular nutritional needs and provide sufficient feed for all the fishes in the tank.

How To Tame An Aggressive Fish?

One thing that causes fights in fishes is when there is at least one aggressive fish in the tank. This can be horrific as nothing will end the fight except when you intervene, or one of them becomes injured and eventually dies. This situation is one of the owner’s worst nightmares, and they try as much as possible to end the fights. This section will provide some tips to help you tame an aggressive fish and have a peaceful tank.

Some fishes are aggressive due to their kind of nature. For example, the tiger barb is a fish whose way of having fun is generally borderline to other species. This means that having a tiger barb and other calm fish will lead to aggressive tendencies. You can, however, tame your tiger barb by introducing more of the species that it can play with. This distracts them from other species as they will be busy themselves all day. Practicing schooling can also help.

While schooling does help for aggressive fishes that are social, this technique fails for aggressive, solitary fishes like the Beta fish. The best method is to install a breeding net that separates the aggressive one from the docile or similarly aggressive fish. If you do not like this idea, you can decide to change your aquarium landscape and have something that is filled with plants and hideouts. This helps obstruct the sightline of fishes, provide hideouts, and can completely halt confrontations.

Hazel Buckley
Hazel Buckley

About Hazel Buckley
Hazel is an animal enthusiast and educator who grew up on a farm which her parents owned in Ingogo, KwaZulu-Natal, South Africa.  The farm was situated right under the Majuba Mountains - the site where the Anglo-Boer War was fought. 

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