How To Easily Calm An Aggressive Guppy!

Common signs of guppy aggression include tail fanning, chasing, and fin nipping, with causes such as stocking issues, male-to-female ratio, food scarcity, lack of hiding spots, poor water parameters, and health problems.

Adjusting your guppy stocking levels, either by increasing or decreasing as needed, can be an effective way to reduce guppy aggression. I’ve found that adding more guppies to my tank significantly lowers their aggression levels.

Incorporating hiding spots and sight breaks, such as live plants, driftwood, and rocks, can also quickly and easily help calm your guppies.

Cause Of AggressionTreatment
Stocking IssuesAdjust Your Stocking As Required
All-Male TankAdd Hiding Spots, Adjust Stocking
Male To Female RatioAdd More Female Guppies
A Lack Of FoodIncrease Feeding Frequency
A Lack Of Hiding SpotsAdd Plants, Rocks, And Driftwood
Water ParametersTest The Water And Correct The Issue
Health ProblemsIdentify The Health Issue And Treat It
Common Causes Of Guppy Aggression And How To Prevent Them

Are Guppies Aggressive Fish?

My Guppies In Their Tank

Some light aggression, such as tail fanning and chasing, can be common among guppies. However, they are not overly aggressive and generally do well in community tanks.

Most guppy aggression occurs in species-specific tanks where male guppies try to establish a dominance hierarchy for breeding purposes.

If two male guppies are determined to become the dominant male and neither backs down, the aggression can quickly escalate.

This was exactly the problem I faced: two of my male guppies were vying for dominance and neither would concede.

The aggression started with constant tail-fanning, then escalated to chasing, and eventually to fin-nipping. At that point, I realized I needed to intervene.

What Are Common Signs Of Guppies Being Aggressive?

Guppies In An All-Male Guppy Tank
Guppies In An All-Male Guppy Tank

The most common signs of aggression between guppies include:

  • Tail Fanning
  • Chasing
  • Fin Nipping

While there are several less common signs of aggression that may appear in specific situations, most people will typically observe the behaviors listed above in their guppies.

Tail Fanning

Guppies Tail Fanning

Guppies engage in tail fanning to encourage submission from another guppy without resorting to physical confrontation.

This behavior involves one guppy swimming in front of another and fanning its tail to the side.

The second guppy might respond by fanning its tail back, signaling that it won’t back down, and other guppies in the tank may join in and fan their tails as well.

Both male and female guppies display this behavior to establish hierarchies in the tank, but tail fanning is more common among male guppies.


Guppies Chasing Each Other

Chasing represents an escalation in aggression between guppies, where one or more guppies pursue another around the tank.

This behavior can be common during mealtimes as guppies compete for food, but it can also result from tail fanning if neither guppy backs down.

Typically, the chasing only lasts for a few seconds before the guppies return to tail fanning or resume their usual activities.

However, if the chasing continues for extended periods, it may escalate into fin nipping.

Fin Nipping

Guppies Fin Nipping

Fin nipping is a serious display of aggression among guppies, as it can cause physical damage.

You may observe one guppy nipping at the fins or tail of another, and due to the length of guppies’ fins and tails, this can lead to rips or tears.

These injuries can become infected, requiring treatment to prevent further complications.

Some people suggest giving the aggressive guppy a “time out,” which I’ll discuss later in the article. However, in my experience, time outs didn’t significantly impact my guppies’ behavior.

Why Are My Guppies Being Aggressive?

Guppies In Their Tank
Guppies In Their Tank

The most common causes of aggression between guppies include:

  • Stocking issues
  • Keeping an all-male tank
  • Male-to-female ratio imbalance
  • Lack of food
  • Insufficient hiding spots
  • Poor water parameters
  • Health problems

While there are several less common causes of aggression, most instances of chasing and fin nipping in tanks are due to one or more of the issues listed above.

Stocking Issues

Stocking A Guppy Tank
Stocking A Guppy Tank

Problems with stocking levels are probably the most common cause of aggression between male guppies.

Unlike other fish species, where overstocking typically leads to aggression, understocking is more often the issue with male guppies.

This was the case with my own guppy tank. Initially, I kept three male guppies in the tank but quickly increased my stocking levels due to problems with aggression.

Adding More Guppies To My Tank

I decided to add five more male guppies to the three already in the tank, and after a few hours of tail fanning, the aggression levels significantly decreased.

While there were occasional bouts of tail fanning and minimal chasing, the aggression was far less than it had been before adding the additional guppies.

Instead of constantly battling for dominance, most of the guppies seemed more interested in foraging for food and exploring their tank.

Keeping An All Male Tank

aggressive guppy
My All Male Guppy Tank

Maintaining an all-male guppy tank can be challenging, with aggression issues being quite common if the tank is not setup correctly.

I have a dedicated article detailing how to set up a 10-gallon all-male guppy tank, which may help you address any potential problems with your own tank.

Some of the more common issues are highlighted below, with a lack of hiding spots and sight breaks being the most prevalent problem in all-male tanks, closely followed by issues with water parameters.

Male To Female Ratio

Balancing the male-to-female ratio in breeding tanks can be challenging, with mistakes often leading to aggression among male guppies.

Traditionally, it was advised to keep two female guppies for every male to protect the females from constant harassment, and to ensure there were plenty of females to keep males distracted.

I consulted several friends who breed guppies for advice on preventing aggression in breeding tanks.

Their recommendation was to significantly outnumber the males with females. Both friends suggested the following male-to-female ratios.

14Very Safe
Male To Female Ratio For A Single Male Guppy

They both recommended having at least three female guppies for every male guppy.

This approach helps prevent any single female from becoming the sole focus of the males and also helps mitigate aggression among the males.

They also emphasized that when breeding fancy guppies, they aim for an even higher male-to-female ratio to reduce the risk of fin nipping and potential infections as much as possible.

21Extremely Risky
22Very Risky
Male To Female Ratio For Two Male Guppies

The stocking table above shows how the safety rating for these same stocking levels change when a second male guppy is added to the tank.

Professional farms do 50 females to each male. 

Cory aquarium co-op

I have also seen people report that professional guppy breeding farms will keep 50 female guppies to a single male to maximize the fry production in the tank.

A Lack Of Food

Fluval Bug Bites Pellet Sizes

Feeding your guppies the right amount can be challenging, with both overfeeding and underfeeding being common issues.

Underfeeding can lead to aggression, as guppies become protective of the limited food available.

I typically feed my guppies twice a day, but I have kept them long enough to know the right amount.

If you are new to keeping guppies, try to remove any uneaten food from the tank within 5 minutes and gradually reduce the amount you feed them until they can eat everything within that time frame.

Here are some food products my guppies really enjoy:

  • Fluval Bug Bites
  • Baby Brine Shrimp
  • Frozen Daphnia
  • Frozen Cyclops
  • Frozen Bloodworm

Bug Bites are definitely the preferred food for my guppies. Unlike my other fish, my guppies tend to let the Bug Bites sink, soften with water, and then eat them.

Baby brine shrimp and frozen daphnia are close seconds when it comes to feeding my guppies, so you can try these foods as well.

Hiding Spots

Hiding Spots In My Guppy Tank
Hiding Spots In My Guppy Tank

A lack of hiding spots and sight breaks can elevate stress levels in your guppies, leading to increased aggression.

I always include live plants in my aquariums, and my guppy tank is no exception.

Live plants not only offer practical benefits for maintaining water parameters but also provide numerous hiding spots and sight breaks.

I have a dedicated article on using live plants in guppy tanks, where I discuss my preferred plants for guppies, most of which are very beginner-friendly.

Hiding Spots And Sight Breaks
Hiding Spots And Sight Breaks

In the photograph above, you can see a top-down view of my guppy tank. The overlaid red circles highlight the areas containing live plants, rocks, or driftwood.

As shown, there is plenty of cover in my tank to help keep my guppies calm and reduce aggression.

Poor Water Parameters

Guppy Tank Water Parameters
Guppy Tank Water Parameters

Problems with water parameters in guppy tanks are common, with high levels of ammonia, nitrite, and nitrate causing your guppies to become agitated, stressed, and aggressive.

I aim to keep the water parameters of my guppy tank within the following ranges:

  • Water Temperature: 63-82°F (17-28°C)
  • Water Flow: Still to Low
  • pH: 7-8.5
  • GH: 8-12 dGH
  • KH: 4-8 dKH
  • Ammonia: 0
  • Nitrite: 0
  • Nitrate: <10ppm

Live plants help maintain lower ammonia, nitrite, and nitrate levels in the tank, in addition to providing great cover and hiding spots.

Ammonia and nitrite levels should be managed by the beneficial bacteria in your tank, provided it is established and the bacteria colonies have had time to develop.

As I mentioned earlier, I committed to daily 30-50% partial water changes in my guppy tank when increasing the stocking levels. This is because the bacteria colonies need time to adjust to the increased bioload and effectively manage ammonia and nitrites.

Health Problems

The vibrant colors and patterns of guppies come at a cost, as the species has been heavily inbred over the years, leading to common health problems.

In addition to genetic weaknesses, the larger fins and tails of guppies make them more susceptible to fin and tail rot.

Health issues are common in guppies, and sometimes aggression can be a symptom of a sick fish.

I take a few minutes each day to inspect all of my fish for any obvious problems, giving me as much time as possible to address any issues.

The challenge is that most fish health problems require different treatments, so accurately identifying the issue is crucial.

Once you are confident in your diagnosis, consider quarantining the affected guppy and starting your treatment plan.

With any luck, the guppy will make a full recovery, and its aggression levels should decrease as it returns to full health.

Final Thoughts

Managing aggression among male guppies can be achieved by increasing stocking levels in the tank, allowing a dominance hierarchy to form naturally.

Common signs of guppy aggression, include tail fanning, chasing, and fin nipping with common causes of guppy aggression include stocking issues, male-to-female ratios, food scarcity, insufficient hiding spots, poor water parameters, and health problems.

I hope that my experiences help my readers facing similar challenges in their own tanks by helping you identify the root cause of the aggression and taking appropriate steps to maintain a harmonious guppy tank environment.