How To Tell If Your Piranha Is Sick {Top 21 Signs and Treatment Options}

Do you believe the abnormal behavior or appearance of your piranha means that a sickness has taken over? What are the signs of illness and how can they be treated? In this article, we’ll discuss the ways to tell if your piranha is sick.

How to Tell If Your Piranha Is Sick: Your piranha’s outward appearance and overall behavior will show abnormalities if it’s sick or becoming inflicted with a fungal or bacterial infection. Check the gills, eyes and swimming patterns. Most of all, check the water quality for spikes in ammonia, nitrites, acidic water and temperatures that are outside of their comfort zone. 

How Do I Know If My Piranha Is Sick?

Is your piranha swimming effortlessly and steadily with its fins erect or is something looking off about the swimming pattern? Let’s look at some signs in a piranha’s behavior and appearance that may indicate if its sick.

A piranha that is sick may show these symptoms:

  1. loss of appetite
  2. gills appear dulls or white
  3. body contours are not well-filled (skinny appearance)
  4. not alert or looks disinterested 
  5. labored breathing
  6. gulping at the surface for air
  7. erratic swimming patterns
  8. swims effortlessly and steadily
  9. drooping fins
  10. loss of balance
  11. swimming on its side
  12. separated from the school
  13. hiding or remaining in the corner
  14. flashing, scraping, scratching against objects or glass
  15. fins are clamped
  16. black patches
  17. missing scales
  18. bulging eyes
  19. cloudy eyes
  20. white specs around eyes
  21. excessive mucus on gills or body

The list could get even longer. Your best skill as an aquarist is your keen eye and perception that something is abnormal about your tank’s ecosystem or the appearance and behavioral changes in your piranhas and other aquatic life.

Why Is My Piranha Sick?

There are plenty of reasons why your piranha could have gotten sick. One common reason is feeding them too many live feeder fish that may arrive with unseen internal diseases. Once your piranha consumes them, the diseases may transfer over.

Here are some of the other main reasons why your piranha might have gotten sick:

  • ammonia poisoning
  • nitrates too high
  • poor pH balance
  • alkalinity is off
  • filter’s media doesn’t contain enough beneficial bacteria
  • tank isn’t cycled properly
  • leftover food spiked ammonia levels 
  • stress from tankmates
  • tank is too small (you need 20-30 gallons minimum per piranha)
  • old age
  • injury
  • skin irritation
  • parasites
  • bacterial infection

What Can I Do For My Sick Piranha?

Your piranha is a messy eater that leaves leftovers. This debris can result in ammonia spikes. Perform 15-25% water changes for a healthy piranha and increase this amount up to 50% if you notice any symptoms of illness.

Clean the gravel with a gravel vacuum. Make sure the tank is large enough. 20 gallons for one piranha is on the small side.

Increase to 30 gallons if you can, but keep in mind that piranhas like to be in groups. They could be healthier in the long-run with an increase of strength in numbers. For 5 piranhas, you’re looking at large tank over 100 gallons.

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Why Is My Piranha Swimming At The Surface?

Your piranha is giving you a clue that something is wrong with the water. There could be a lack of oxygen or the temperature is off. Oxygen deprivation or a toxicity in carbon dioxide is obvious when your piranha is gulping for air at the surface. Other possibilities include;

  • parasitic infection in gills
  • high nitrites and ammonia
  • acidic water (high pH)
  • increased respiratory rate (rapid gill movement)
  • skin flukes
  • Ich (protozoan white spot disease)

It’s time to either visit the vet or seek treatment options for your piranha. You may have to treat the tank as a whole instead of focusing on one sick fish.

How Do I Treat A Sick Piranha?

Start with performing larger water changes. You can also consider the following options:

  • Aquarium Salt: good for stress reduction, fungal and ich related remedy.
  • Coppersafe: helps with parasites, ich, flukes, anchor worms, velvet.
  • Maracide: assists with extra mucus, visible spots or worms, rapid breathing, flashing.
  • Melafix: antibacterial remedy for damaged fins, wounds, ulcers, fungus, fin rot.
  • Pimafix; treatment for fungal, internal and external bacterial infections.
  • Potassium Permanganate: treats pathogens and a wide range of infections.
  • Prazipro: Helps eliminate parasites flukes and tapeworms among other illnesses.
  • Tetracycline: Popular with bacterial infections, fin rot, frayed fins, inflamed gills, open sores.

Your local fish shop and veterinarian will assist in providing their opinion on the best course of treatment depending on the conditions or symptoms present.

What Do I Do If My Piranha Is Wounded?

A wounded piranha runs the risk of being eaten by other piranha tankmates. Remove this piranha for now and place it in a quarantine or hospital tank. Use a broad spectrum antibiotic to prevent further infection.

Look for lesions, swellings, discoloration and long stringy feces. Offer protein rich foods such as krill and bloodworms along with blended cichlid pellets. Avoid live feeder fish for the possibly that they may carry diseases from unknown sources.

Why Is My Piranha Swimming Sideways?

A piranha swimming sideways is symptomatic of swim bladder disease. The swim bladder is full and is causing your piranha to swim off balance. This affects buoyancy.

Bloating or constipation may push against the swim bladder. Your piranha may sink to the bottom of the tank or float up. Seek treatment for swim bladder disease as soon as you notice this behavior.


You may be able to save your sick piranha if you act in time. Check your water quality first and see if it needs adjustments with water changes or filtration.

Offer medication or nutrient rich food during this time. You can soak the food in liquid garlic to boost their immune systems and entice them to eat more.

Your veterinarian that you trust should be consulted if symptoms do not improve. We hope your piranha recovers quickly and continues to live out its long lifespan which could surpass a decade in your spacious and healthy tank.


Thanks for visiting for another article on Piranhas that we greatly enjoy taking care of in our aquariums. Check out more of our articles on the variety of aquatic life we research and keep. Bye for now!

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.

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