Are Fantail Goldfish Aggressive: Common Reasons and Solutions

The fantail goldfish is a relatively small fish that can be aggressive when kept in a small space. This aggression may manifest as body biting, spitting, and chasing other tankmates. If you are only keeping one fantail goldfish, keeping them in peace should not be difficult. In addition, the fantail goldfish is an active fish that needs plenty of room to swim and play. If you have a smaller tank, it may be best to keep the fantail goldfish on its own.

The General Nature of Fantail Goldfish

Goldfish are gentle, peaceful creatures in many different colors and shapes. They’re gentle enough to be kept in an aquarium but can become aggressive when their territory is violated or feel threatened. If you find that your goldfish is becoming aggressive, there are some steps you can take to help settle the situation. 

For starters, ensure your fish is healthy and happy by providing plenty of food and water and an environment that’s comfortable for them. If that doesn’t work, you can try keeping them in a separate tank or aquarium.

You can try sedating or tranquilizing your fish if that’s still not enough. If all else fails, you can try relocating them to a new home. Goldfish are naturally territorial and may become aggressive when they feel threatened or if their territory is violated. So, if you’re ever having trouble with your goldfish, remember to keep things calm and peaceful by following some of these tips.

Reasons Why Fantail Goldfish Can Be Aggressive

There are a few reasons why your goldfish may become aggressive, and often these issues can be solved by following a few simple tips.


One common issue is overcrowding, which can lead to territorial behavior. If you notice your fish becoming aggressive, the best solution is to transfer some of the weaker fish over to a separate tank so that the dominant one doesn’t have as much territory to defend. If that doesn’t work, gradually introduce new tanks bit-by-bit over a few weeks rather than all at once to avoid any potential conflict escalation. Finally, ensure your water temperature maintains a stable 61 – 77 degrees Fahrenheit throughout the year – high temperatures (over 80 degrees) lead to aggressive behavior in goldfish.

Mating Behavior

Goldfish are notorious for their aggressive mating behavior. If you don’t want your goldfish to fight constantly with each other, it is essential to provide them with a territorially-defined space. Goldfish also have a mating ritual where the male goldfish courts the female with lavish displays of color and movement. Do not feed live fish to your goldfish – they will eat each other and ultimately you. If you wish to keep goldfish as pets, get them into a community tank so they can’t monopolize all the space.

Small Living Space

Fantail goldfish make great house pets but need a lot of space to live in. You can provide them with a smaller tank or add more fish to their existing tank. If your goldfish doesn’t have enough space, it may become aggressive towards other fish in the tank and eventually get put down. Goldfish also require ample water to swim in and play around in – so be sure you’re providing enough for them.

Limited Food

Like all fish, goldfish need food to survive. However, they will become aggressive if they don’t have enough to eat. Try to provide them with a variety of foods and ensure you’re providing enough food for them at all times. If their living space is limited, it may also affect how much they can eat and how active they are in the tank.

Crowded Conditions

Goldfish are social animals, and they tend to get along well when they’re in a crowded tank. However, if your goldfish lives in an overcrowded tank, it may become aggressive. If problems persist, it might be time to get another type of goldfish or find a new home for your existing fish. Instead, try moving some fish into smaller tanks or create more space for them by adding gravel or plants.


A goldfish is a beautiful and gentle fish, but that doesn’t mean it can’t get aggressive. If your fantail goldfish starts attacking other fish or people in its aquarium, it’s time to put it down. There have been cases where these fish have attacked other fish in the tank – usual fantails of the same species. However, there is no surefire way to prevent disputes from happening, so be aware of the signs and take action if necessary.

Unsuitable Tankmates

Goldfish are finicky fish and do not like living with other fish. If you cannot find a suitable tank mate for your goldfish, keeping them in a separate tank is best. A fantail goldfish can get along well with other small water creatures but should be avoided with larger fish species. Feeding your goldfish a varied diet will keep them healthy and less likely to become aggressive towards other fish in their tank.


Startled fish can be a real nuisance. They may become aggressive and territorial when they feel threatened or have their own space to protect. If you don’t handle these situations correctly, you could end up with an altercation on your hands. To avoid such a scenario, keep your fish well-lit and spacious, so it has enough room to swim freely.


Stress is one of the most common problems faced by fish owners. It can be caused by various factors, including overcrowding and low oxygen levels. When stressed, goldfish are more likely to bite people or animals they come into contact with. For example, suppose you notice your goldfish behaving unusually or biting people. In that case, it’s best to get them out of their aquarium and tank as soon as possible and transfer them to a freshwater environment.


Goldfish are territorial animals and will defend their territory against other fish. Introduce new goldfish slowly into the territory, so they do not get stressed out. Instead, provide plenty of hiding places for the goldfish in its territory to feel secure. If you try to move a goldfish from its territory, it may become aggressive.

What Should I Do If My Fantail Goldfish Is Aggressive?

If your goldfish is exhibiting aggression, you should immediately remove it from the aquarium. Aggressive fish can injure or even kill other fish in an aquarium, so it’s best to take them out before they do too much damage. 

If possible, try to calm the fish down and establish a peaceful environment for it in another tank or enclosure. You may also need to feed your goldfish a varied diet to keep them healthy and less likely to become aggressive towards other inhabitants of their home.

In addition, make sure the aquarium is well-lit and spacious so that the fish has enough room to swim freely. Leaving goldfish in small enclosures can lead to aggressive behavior.

Can You Keep Fantail Goldfish With Other Fish?

Yes, fantail goldfish can coexist peacefully with other fish in an aquarium, provided they have plenty of space. So provide your goldfish with a spacious territory and plenty of hiding places to ensure it feels safe. It depends on the tank size and water quality of the fish you intend to keep.