Goldfish chase each other in an overcrowded aquarium to establish dominance or during feeding time. Male goldfish chase females as part of their mating ritual during the breeding season. Some goldfish also like to bully others by chasing them. Sick and weak goldfish get chased by the stronger ones.
Let’s now talk about all the reasons for goldfish to chase each other.
Main Reasons Why Goldfish Chase Each Other In A Tank
Due to their peaceful disposition, goldfish are suitable for community tanks.
If you offer enough food and maintain the tank well, this fish will thrive and not cause any trouble.
However, they act out and become aggressive under certain circumstances. Let’s look at the circumstances that trigger this type of behavior.
Breeding season.
If you have both male and female goldfish in your aquarium, the males will chase the females during the breeding season.
The males will relentlessly pursue the females. You will most likely notice this weird behavior because it can go on for hours.
When a male goldfish senses that the female is ready to spawn, he starts following her.
By chasing the female all over the tank, he encourages her to release her eggs.
This mating ritual is very tiring, and both fish get exhausted by the end of it.
Nevertheless, it can go on for several hours until the female succumbs and releases her eggs into the water.
During the ritual, the male may also nip the fins and tail of the female. It will look like the fish are fighting.
However, at the end of the chase, the female will release her eggs into the water.
The male will then fertilize the eggs by releasing his milt over them.
The tank water will turn cloudy when the eggs are being fertilized.
However, the cloudiness will recede in a short while, and the water will become clear.
Overcrowding.
Each goldfish needs ten to twenty gallons of water to live comfortably in a tank.
They don’t do well in overcrowded tanks. Although goldfish may survive in a small tank, it’s not an ideal environment for the fish.
Living in an overcrowded tank can bring out undesirable behavior in these fish.
They may start competing for space and become aggressive towards their tank mates.
The stronger and bigger fish may bully the smaller fish and chase them around.
Assess the space requirements of your tank if your goldfish are chasing each other.
You may have to upgrade to a bigger tank or move a few fish to a separate tank if the existing tank is too small for all of them.
Sickness and injury.
Unfortunately, goldfish are not very empathetic. They will bully and hurt any injured or ill fish they come across.
When strong fish peck on the weak ones, the weaker fish become stressed.
Their aggression can also cause further physical damage to an injured fish.
Hence, it is a good idea to quarantine any sick or injured goldfish in a separate space.
Once it fully recovers, you can return it to the original tank.
Physical characteristics.
Goldfish are fin nippers. They are attracted to the long flowy fins and tails of their tank mates.
So, the slower goldfish with long flowing fins and tails can become an easy target for the others.
Due to their enormous fins and tail and slow speed, fancy goldfish have a more challenging time when housed with common goldfish.
Smaller and faster goldfish will pursue them and nibble and peck at their beautiful appendages, causing them stress.
Territorial behavior.
Some goldfish can be hostile towards new fish that appear in their tank.
They may feel threatened and act out by bullying and chasing the new fish. However, this aggression is usually short-lived.
Their attitude should improve over time.
Nevertheless, be on the lookout for trouble. If the fish keep fighting, one or both may get seriously injured.
You can also put the troublemakers in “time-out” when they get too aggressive.
When you re-introduce them into the tank, they will have calmed down.
You can also consider adding more plants or decorations to your tank.
It will offer more hiding spots for the small or weaker fish to avoid their attackers.
Competition for food.
Goldfish are ravenous fish. They constantly search for food and eat several times a day.
They don’t like to compete for food and can become aggressive if they don’t get enough food.
If your tank is overcrowded or you do not feed your goldfish well enough, they may become aggressive.
If your fish start fighting and chasing at mealtime, it could be because you don’t provide enough food for all the fish.
Try offering more food and see if it resolves the issue.
However, if you increase the amount of food and the behavior continues, lack of food may not be the issue.
Try separating the fish while feeding them and check if it solves the problem.
Why Do Goldfish Chase Each Other In A Pond?
The behavior of goldfish and koi in ponds resembles that of the goldfish we keep in our aquariums at home.
Although they are usually bigger than the ones in tanks, they share the same behavioral tendencies.
In a pond, overcrowding rarely occurs. The fish will have enough space to swim and enjoy their surroundings.
So, they will not fight with each other for lack of space. Natural ponds will also have enough food sources.
Hence, the fish will not struggle or fight for food.
Nonetheless, you may notice pond goldfish chasing each other. This is usually during their breeding time.
Spawning season is usually from May to June. During this time of the year, pond goldfish may seem aggressive.
You can see the males chasing the females for several hours. There will be a lot of frantic activity in the pond.
It’s safe to assume that the fish are spawning if many of them are acting differently at the same time.
At the end of all this chaos, the females will release their eggs into the water.
The freshly laid eggs will stick to different surfaces of the pond, like the sides and rocks.
After the females release the eggs, the males will fertilize them.
The fish should resume normal behavior after these activities end.
The water in the pond at this time may appear different. If your pond has clear water, it will turn turbid during spawning.
The pond’s surface may become foamy when the fish release their eggs and milt into the water. You may also sense a change in odor.
However, these changes are temporary, and you don’t have to do anything.
It will clear on its own after the process.
Although it may take a day or two, the pond water will get back to normal once the eggs are fertilized.
Just let nature do the job, and your water quality will be back on track in a short time.
However, if it’s an artificial pond and you use filters to maintain cleanliness, you may have to clean the filter media after the spawning occurs.
