As someone who has kept guppies for over 20 years and owned a pet shop specializing in tropical fish, I am often asked if guppies are aggressive. From personal experience, I can tell you that guppies have a reputation for nipping fins and being bullies in the aquarium, but the reality is more nuanced. In this blog post, I’ll share my wisdom and personal stories to explain guppy behavior, both towards other fish and each other. Read on to get the real scoop!

My History with Guppies

I first became obsessed with guppies as a young boy around 8 years old. I loved their colorful tails and active behaviors. I convinced my parents to let me set up a small 10-gallon tank to house my first guppies. I’ll never forget the excitement of picking out three male fancy guppies from the local pet shop to start my colony.

Over the years, my guppy tanks grew bigger and my colonies expanded. I learned all about the different tail types, color strains, and how to breed show-quality guppies. Now, over 20 years later, I have an entire fish room dedicated to guppy breeding and sell my homebred strains in my pet shop. Suffice to say, I have a lot of personal experience when it comes to guppy temperament from keeping them with various tank mates over decades.

Guppies with Other Fish

Due to their stunning appearance and peaceful demeanor, guppies are one of the most popular freshwater community fish available. This leads new aquarists to assume guppies can be kept with any other fish. However, looks can be deceiving, and guppies have a reputation for fin nipping.

Through years of experimentation, I have found the below types of fish that do well with guppies:

• Small tetra species (neons, cardinals, embers)
• Corydoras catfish
• Dwarf cichlids (apistogramma, kribensis, rams)
• Plecostomus catfish
• Otocinclus algae eaters
• Certain livebearers (platies, swordtails, mollies)

The key is choosing tank mates that won’t nip fins and are not aggressive themselves. Slow swimmers with short flowing fins, like bettas or angelfish, unfortunately do often fall prey to guppy attacks, so I do not recommend combining them.

Additionally, tank size plays a role. The more cramped the quarters, the more territorial fish become, including guppies. Make sure your community tank allows each fish adequate space and line of sight barriers with plants and decor. This diffuses aggression and allows timid species places to hide if picked on.

Molly Fitzgerald’s Case of the Killer Guppies

I’ll never forget my longtime customer Molly Fitzgerald coming into my shop nearly in tears over her “killer guppies.” Molly explained she had set up a 15-gallon community tank with three male guppies, three panda cory cats, and three glowlight tetras. Within two days, the fins of her tetras were shredded and the cory cats had visible bites on their tails.

I asked Molly to bring me one of the offending guppies. Under the magnifying glass I could see this male had unusually large jaws and an aggressive demeanor, flaring his fins at my finger. I determined she just had an unusually pugnacious guppy strain in that group.

I had Molly do a series of water changes to heal her injured fish while I bred her several mild-mannered feeder guppies. Within a week her tank dynamic totally transformed into the peaceful community tank she had dreamed of!

This story illustrates individual guppy temperaments can vary drastically, from placid to feisty. While most fancy strains sold in shops tend towards passivity, occasionally “killer” personalities crop up, especially in feeder strains not bred for temperament.

Guppies Amongst Themselves

Guppies are a “harem” fish species, with one male establishing dominance over a group females in the wild for mating privileges. This triggers some level aggression amongst males competing for mates, establishing territories, and even harassment of females.

In captivity if male to female ratios become skewed, the dominant male can terrorize females to the point of declining health or death in extreme cases. Alternatively, too many males crammed together heightens aggression between all guppies over perceived breeding rights.

Best practice is keeping two females per male in a colony. Provide plenty of bushy plants for females to hide if pestered. Target ratios should be:

2-3 Females per Male in 10 Gallons
3-4 Females per Male in 20 Gallons
4-6 Females per Male in 30+ Gallons

Culling Overly Aggressive Guppies

As a guppy breeder, managing aggression is crucial for colony health. I remove any guppies showing signs of antisocial behavior like constantly flaring gill covers, chasing, fin nipping, or indicators of stress in tankmates like clamped fins or hiding. Removing bullies keeps the peace while culling undesirable aggressive traits from future breeding pools.

While euthanizing fish is never pleasant, responsible culling helps maintain docile, community-friendly strains. This process over generations has allowed me to offer customers guppies renowned for their pleasant temperaments and dazzling colors.

The Bottom Line on Guppy Aggression

Guppies may have a bad rep in some circles for fin nipping and bullying. However, through careful selection of tank mates, appropriate male to female ratios, roomy aquariums, and conscientious culling, guppies can make exquisite peaceful additions to community tanks.

While individual aggressive guppies occur, especially in feeder strains, the vast majority of fancy guppies have been carefully bred for generations specifically for their tranquil and active behaviors in home aquariums.

So take guppy aggression reports with a grain of salt! Have reasonable expectations for their behavior, provide them adequate space, and select compatible tank mates, and you are highly likely to enjoy their gorgeous colors and energetic antics lighting up your freshwater community tank.

I hope sharing my 20+ years of experience eases concerns over guppy temperament. Please feel free to contact me if you have any other questions – happy fishkeeping!

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