As a goldfish keeper, you must be surprised to see your goldfish rubbing against each other. So, why are my goldfish rubbing against each other? Is it normal? Let us find out:
Goldfish rubbing against each other indicates mating behavior as the male rubs against the females to make her lay eggs. Contaminated water and incompatible tankmates can also promote such goldfish behavior. Provide favorable water conditions and ample space to prevent such behavior of your fish.
The below article, we will discuss all the reasons behind your goldfish rubbing against each other. In addition, we will also learn about the measures you should take to prevent such issues in your fish.

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My goldfish is rubbing against each other
Your goldfish rubbing against each other indicates mating behavior in your goldfish.
However, such behavior can also indicate aggression in your goldfish.
Although goldfish are non-aggressive species, they can turn aggressive in an overcrowded tank.
Pairing common and fancy goldfish can also lead to aggression in the tank, eventually making your goldfish rub against each other while competing for food.
Your goldfish rubbing against each other also indicate the playful behavior of your fish as goldfish are active species that love to interact with their tankmates.
Is it normal for your goldfish to rub against each other?
It is normal for your goldfish to rub against each other while mating. Your male goldfish rub against the female to make her lay eggs.
You can easily detect the mating behavior as the female goldfish will be broader than usual while she is about to lay her eggs.
However, if you discover the two males rubbing against each other, it indicates aggression in goldfish.
Despite being peaceful, many factors like an overcrowded tank can make your goldfish aggressive with their tankmates.
Pairing your goldfish with aggressive fishes like betta can also lead to aggression in the tank.
In such a case, you should take immediate action as ignoring such a situation can lead to severe injury in your goldfish.
Also read: Can Goldfish Get Pregnant?

What are the reasons behind your goldfish rubbing against each other?
Here is the reason behind your goldfish rubbing against each other
- Your goldfish is mating
- Your goldfish has turned aggressive
- Your goldfish is playing.
Mating
Mating is the most common reason behind your goldfish rubbing against each other.
The male goldfish chases the female and rub himself against the female to encourage her to lay eggs.
Once the female goldfish lays her eggs, the male fertilizes the eggs by releasing their milt upon the eggs.
Aggressive
Aggression can also be a reason behind your goldfish rubbing against each other.
Despite being peaceful species, your goldfish can turn aggressive due to many factors like
- Poor Water Condition
- Overcrowded Tank
- Pairing the common and fancy goldfish together
Poor Water Condition
Contaminated water can drop the tank’s oxygen level, making your goldfish stressed and aggressive.
Poor water conditions can also lead to severe health issues like swim balder disease in your goldfish.
Contaminated water can also lead to a spike in the ammonia levels making the tank’s water highly acidic, eventually affecting the gills of your goldfish.
Overcrowded Tank
An overcrowded tank can also make your goldfish territorial and turn aggressive towards each other.
An overcrowded tank also affects the growth of your fish, leading to stress in your goldfish.
Pairing the common and fancy goldfish together
Pairing common and fancy goldfish together can make your fancy goldfish compete for food, eventually leading to aggression.
Slim bodied goldfish are faster than fancy goldfish making your fancy goldfish compete for food in the tank.
Pairing them together can lead to severe injuries to fancy goldfish as they are delicate.
Also read: Can Common Goldfish Live With Fancy Goldfish?
Playful
Your goldfish rubbing against each other also indicates the playful nature of your fish.
However, if you discover nipping, it indicates aggression in the tank.
Ignoring such a situation can lead to severe injuries to your fancy goldfish, eventually leading to the passing away of your goldfish.

How to prevent such issue in your goldfish?
Here are ways to prevent such issues in your goldfish
- Provide Good Water Quality in the tank
- Avoid overstocking your tank.
- Pair your fish with compatible tankmates
Good Water Quality
You should provide good water quality to your goldfish to avoid such issues.
Goldfish produces a lot of waste in the tank resulting in the spike of toxic chemicals.
You can add a water filter to your goldfish tank to keep the tank’s water clean and eliminate the water’s harmful chemicals.
Particulars | Goldfish |
---|---|
Ammonia Levels | 0-0.25ppm |
Nitrate Levels | 0-40ppm |
You can test the ammonia levels with the help of an ammonia test kit.
We suggest you to use API Ammonia test kit as it provides accurate result.
You can buy if from Amazon: API TEST KIT
Also read: Can Goldfish Survive In Dirty Water?
Avoid Overstocking
You should avoid overstocking your goldfish tank to prevent such issues.
Overstocking makes your goldfish turn territorial and affects your fish’s growth.
We advise you to provide ample space in your goldfish tank for your fish’s proper growth and development.
Types of Goldfish | Minimum Size | Maximum Size | In a 10-Gallon Tank |
---|---|---|---|
Common Goldfish | 4 inches (10.16cm) | 14 inches (35.56cm) | 1-2 small Goldfish |
Shubunkin Goldfish | 9 inches (22.86cm) | 18 inches (45.72cm) | 1 small Goldfish |
Sarasa Goldfish | 4 inches (10.16cm) | 14 inches (35.56cm) | 1-2 small Goldfish |
Comet Goldfish | 2 inches (5.08cm) | 12 inches (30.48cm) | 1-2 small Goldfish |
Fantail Goldfish | 6 inches (15.24cm) | 8 inches (20.32cm) | 1-2 small Goldfish |
Also read: How Many Goldfish Can You Keep In A 10-Gallon Tank?
Pair with compatible tankmates
It would be best to pair your goldfish with compatible tankmates to avoid such behavior of your fish.
Pair your slim-bodied goldfish with fancy goldfish can lead to aggression while competing for food. It is because fancy goldfish are delicate and slower than common goldfish.
We advise you to place your goldfish with peaceful species like guppy to avoid such issues in your fish.
Pairing your goldfish with another peaceful species will also help develop a healthy environment in your goldfish tank.
Also read: Can Goldfish Live With Guppy?
Conclusion:
- Your goldfish rubbing each other usually shows the mating behavior of your fish.
- Many different factors like poor water quality and overstocking can also make your goldfish aggressive towards each other.
- Avoid pairing your slim-bodied goldfish with fancy goldfish to prevent such issues in your goldfish tank.
- Always maintain adequate water conditions to prevent such issues.
- Always provide a suitable size tank to your goldfish for their proper growth and development.
Reference: ScienceDirect