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Home > Goldfish > How to Handle a Goldfish Emergency: 13 Solutions & Prevention (Vet Answer)

How to Handle a Goldfish Emergency: 13 Solutions & Prevention (Vet Answer)

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Dr. Luqman Javed

Veterinarian, DVM

The information is current and up-to-date in accordance with the latest veterinarian research.

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It can be distressing when you find any of your pets struggling, but unfortunately, emergencies do happen. When your goldfish is experiencing an emergency, quick intervention can help them survive in some instances.

In this article, we go over what might be wrong with your fish and methods that can help in most goldfish emergencies. Hopefully, your pet will pull through in the end!


What Is a Goldfish Emergency?

In the simplest terms, a goldfish emergency is any injury or illness that poses an immediate risk to your goldfish’s life or long-term health. As the name suggests, quick intervention in these situations is key, and fortunately, most goldfish emergencies are entirely preventable with the correct setup.

The 13 Common Emergencies Explained

Let’s explore the common goldfish emergencies and what you can do to mitigate them.

1. Ammonia Poisoning (New Tank Syndrome)

Lionhead goldfish died due to poor water quality or ammonia poisoning
Image By: Zay Nyi Nyi, Shutterstock

This is the most common emergency you might encounter as a beginner to the hobby. Placing goldfish in an aquarium that isn’t cycled can cause a sudden spike in ammonia levels in the water, as fish produce ammonia as a natural byproduct of their metabolism. Depending on the size of the aquarium, the number of goldfish you place in the aquarium, and the pH of the water, your fish may show signs in as little as an hour to within a day.

Unfortunately, mortality rates are very high; it’s not uncommon for new fish keepers to wake up to a tank full of dead fish.

An ammonia spike can also occur if you are overly enthusiastic about cleaning your aquarium and accidentally remove the beneficial bacteria from the filter (either by overcleaning the filter cartridges or by using certain cleaners not safe for them, such as bleach).

Signs of Ammonia Poisoning:

  • Sudden death
  • Erratic swimming patterns (also known as flashing)
  • Lethargy
  • Poorly coordinated swimming
  • Refusal to eat
  • Heavy breathing
  • Gills appearing red
  • Gasping at the surface (also known as piping)

How to Confirm:

  • Test the water for ammonia levels. Any reading over 0 is considered not ideal for pet fish.

What to Do:

  • Immediately perform a large water change of around 30–50%.
  • Water changes and ammonia tests should be repeatedly performed until ammonia levels are at 0 ppm or 0 mg/L (depending on the kit you use). Depending on the size of your aquarium, you might have to change the water every 4–6 hours in order to keep your fish safe.
  • Stop feeding your fish temporarily.
  • If your tank is overstocked, consider reducing the stock size by moving some fish to another tank. Alternatively, switch to a larger tank.
  • Heavily oxygenate the water using air stones and powerful filtration.
  • If your tank’s pH is alkaline (over 7.0), use a product to bring it as close to 7.0 as possible.
  • Add commercial ammonia binders, aquarium salt, and nitrifying bacteria. Follow the dosing instructions on the product labels. Some products might require carbon filtration to remove them from your aquarium. Activated carbon can be added to most filtration systems to do so.
  • Contact your aquatic veterinarian for any secondary issues or diseases that occur due to the poisoning.

How to Prevent It:

  • Only add goldfish to an appropriately sized aquarium that is cycled. This ensures that the bioload on the tank isn’t too high and there are sufficient bacteria in the filter and on other surfaces in the aquarium to handle the waste produced by your goldfish.
  • Do not use chemicals or attempt to “scrub” the biological media cartridges in your filter.

2. Nitrite Poisoning

This is very similar to ammonia poisoning, as ammonia is converted to nitrite as part of the nitrogen cycle. Nitrite is toxic to goldfish as well. The causes for this are very similar to those of ammonia poisoning.

Many of the signs are also similar to those of ammonia poisoning; however, with nitrite poisoning, you might also notice the following:

Signs of Nitrite Poisoning:

  • Heavy breathing, rapid gill movements
  • Fish tend to gather near the filter
  • Gills may appear pale or brown

How to Confirm:

  • Test the water for nitrite levels. Any reading over 0 is considered not ideal for pet fish.

What to Do:

  • Same protocol as that for ammonia poisoning.
  • Aquarium salt is very useful for nitrite poisonings.
  • Bacteria cultures added to the aquarium for nitrite poisoning should include Nitrosomonas (these also metabolize ammonia well) and Nitrobacter strains (these are particularly efficient at metabolizing nitrite).

How to Prevent It:

  • Same as that of ammonia poisoning.

3. Acclimation Shock

Image Credit: Noheaphotos, Shutterstock

This is another unfortunate event that’s easily preventable. Adding fish to a new aquarium is a process that should be done slowly. If fish are introduced to a new source of water with differences in temperature, pH, and other factors, they can sometimes suffer acclimation shock.

Signs of Acclimation Shock:

  • Rapid death after being introduced to a new aquarium
  • Signs of stress or illness

How to Confirm:

  • Confirmation is usually associated with the knowledge that the fish were added to the aquarium rapidly rather than after slow acclimation.

What to Do:

  • If your fish are already in the new aquarium, gently remove them and place them in a quarantine environment with some stress medicine for a period of about three days.
  • Slowly acclimate your new goldfish to the aquarium over a period of about 30–60 minutes using a floating technique.
  • If needed, you can compare the parameters of their container’s water to your aquarium’s water (pH, dissolved oxygen, hardness, salinity, etc.).

How to Prevent It:

  • Always acclimate your fish to new water slowly to ensure they can adjust to changes in the water chemistry well.

4. Water Contamination

Water contamination refers to the contamination of water sources by substances that make the water dangerous for your goldfish.

When dealing with pet goldfish, these are the most common contaminants to be wary of:
  • Chlorine and chloramine
  • Heavy metals dissolved in water
  • Any medicine added to the water that was overdosed or left in too long (copper sulfate, malachite green, formalin, potassium permanganate, antibiotics, etc.)
  • Pesticides (includes pyrethrins and pyrethroids used as medicine for other pets)
  • Nicotine (if someone in your house smokes)
  • Detergents
  • Heavy metals
  • Algae medicine (if overdosed)

Signs of Water Contamination:

  • Signs of distress
  • Erratic behavior or abnormal swimming

How to Confirm:

  • Very difficult to confirm, and contamination is usually determined by tracing historical events or incidents (for example, ask yourself if you forgot to condition the water after a change) and observing fish in distress.

What to Do:

  • Perform repeated water changes (30–50%) on a daily basis until the signs resolve.
  • Contact your aquatic veterinarian if you’re not sure about what contaminated your fish.

How to Prevent It:

  • Always condition any water before placing it in your fish’s aquarium.
  • If you have other pets at home with flea collars or topical flea medications, thoroughly wash and dry your hands and arms before handling your fish, and keep your other pets away from your fish.
  • Nicotine is very toxic for fish; ensure nobody smokes near the vicinity of your aquarium.
  • A UV light in your filter can help neutralize some pathogens and chemicals. Likewise, activated carbon can also help neutralize some toxins.
  • Always seek veterinary advice before medicating your fish. The pharmacokinetics of many drugs used in fish tanks are still not properly understood, and at times, doses which seem normal may be harmful to pet fish.

5. Aquarium Shattered or Cracked

Glass for aquarium cracks
Image Credit: Wikamol D, Shutterstock

This emergency is pretty self-explanatory and usually occurs in aquariums that are moved while full or if something has damaged the structural integrity of your aquarium.

What to Do:

  • Move your fish to a new aquarium promptly.
  • Be very careful when unplugging items near a cracked aquarium; the electrocution risk is extremely high! It is best to switch the power supply off from the main switchboard before attempting to remove any equipment from the aquarium.
  • Be mindful that some aquarium equipment can become damaged or non-functional if not submerged.

How to Prevent It:

  • When setting up aquariums, always fill them with water and check for a leak before adding your fish in.
  • Do not use sharp items to clean the walls of your aquarium. Items such as razor blades can damage the structural integrity of an aquarium (especially a glass aquarium).
  • Try purchasing aquariums from a reputable aquarium manufacturer.

6. Goldfish Jumped Out of Tank

This is pretty self-explanatory as well. Depending on the humidity of the room your aquarium is in, your goldish may have just a few minutes to a few hours before they perish.

What to Do:

  • Pick your fish back up and place them in a quarantine tank. Ensure it has a lid! Do not attempt to “wipe” or clean your goldfish as this may remove their slime coat and make them more susceptible to diseases.
  • Check your water parameters in your aquarium using a test kit; some goldfish jump if they are distressed from ammonia poisoning.
  • Add some stress medication to the quarantine tank and monitor your fish for signs of injury for about a day.
  • Proceed with the treatment of any water quality issues, if needed.
  • Contact your veterinarian if you think your fish has suffered an injury from the fall of the jump.

How to Prevent It:

7. Power Outage

dirty aquarium
Image Credit: Acraveinza, Shutterstock

While a short-term power outage is not a big deal, prolonged power outages can cause a rapid buildup of waste in your aquarium and can also crash your nitrogen cycle by killing the bacteria in your filter.

What to Do:

  • Perform partial water changes to ensure your fish’s water quality stays acceptable.
  • Stop feeding your fish temporarily.
  • If your power outage lasts longer than a day, disconnect your filter and add some fish food to your filter compartments. Fish food can produce some ammonia for your bacteria to sustain themselves.
  • Proceed with the treatment of any water quality issues, if needed.

How to Prevent It:

  • There isn’t much you can do to prevent a power outage; however, a backup power generator can be useful in some cases.
  • Air pumps can be easily damaged during a power outage if they are at a level below your aquarium because water can travel down their connecting tube and into the device. Ensure they are at a level above your aquarium so that gravity will prevent water from reaching the air pump.

8. Equipment Malfunctions

This is a major emergency if the submerged equipment introduces an electric current into your aquarium. Water is an excellent conductor of electricity, and unfortunately, by the time you realize equipment has malfunctioned, your fish are often electrocuted.

What to Do:

  • Disconnect the main power source; do not place your hand in the water without doing this!
  • Remove the faulty equipment. If it has a warranty, send it for repairs. If not, you should discard it.

How to Prevent It:

  • Always source your equipment from reputable suppliers and brands.
  • Ensure you follow voltage instructions when setting up your equipment.
  • Stay on top of routine maintenance for your equipment.

9. Predator Has Access to Pond or Tank

cat aquarium
Image Credit: Maleo, Shutterstock

Fish are prey for many animals, including some pets. If a predator animal (wild or pet) has access to your pond or aquarium, your fish are at risk of being captured.

What to Do:

  • Immediately remove the predator if possible. If the predator is a dangerous wild animal (such as a bear), contact animal control promptly.
  • Count your fish after the incident, and treat any injured fish if needed. Contact your veterinarian if the injuries seem extremely severe. Consider euthanasia for fish that are too injured and may not make it.

How to Prevent It:

  • Ensure your aquarium has a lid and that your pets cannot access it (indoors).
  • A cover for your pond can help prevent predators from accessing the pond. Fences can ward off ground predators.
  • For pond setups, ensure you provide your fish with plenty of hiding spots in the form of caves, rocks, and heavy plantations. Though these aren’t guaranteed to save your fish from a predator, it offers them a better chance of survival.

10. Temperature Extremes

Fish do not respond well to temperature extremes or sudden changes in temperatures. Goldfish that are kept in small aquariums are more vulnerable to this, as the smaller volume of water has the potential to quickly fluctuate in temperature and harm your fish.

Signs of Temperature Extremes:

  • Fish will appear restless and overly active (if too hot)
  • Fish will be lethargic and may not eat (if too cold)
  • Fish may die (if temperature changes suddenly)

How to Confirm:

  • Use a submersible thermometer to check the water temperature.

What to Do:

  • Use either a chiller/fan or an aquarium heater to adjust the temperature to a desirable level. Please note that you should NOT change the water’s temperature by more than 1–2°C (1.8–3.6 °F) per day. A sudden change may inadvertently shock and stress your fish. Gradual changes in temperature are advised for your fish’s safety. It is best to adjust the temperature by 1°C (1.8°F) every 12 hours until you reach the desired temperature.
  • The acceptable temperature range for goldfish, whether they’re kept indoors or outdoors, is 16–22°C (60.8–71.6°F). Fancy goldfish have lower tolerances to changes in temperature and should be kept at 20–23°C (68–74°F). Their optimal temperature for growth, immunity, and reproduction is between 20°C (68°F) and 22°C (72°F).

How to Prevent It:

  • A larger aquarium prevents sudden temperature fluctuations.
  • Depending on where you live, heaters, chillers, or fans can be used to control the temperature in your aquarium or pond.

11. Natural Disasters

Image Credit:, Shutterstock

Unfortunately, there isn’t much that you can do here, but it’s important to note that your fish can likely tolerate periods of fasting in a disaster, and you shouldn’t prioritize feeding them. Instead, you should prioritize following emergency guidelines from your authorities.

What to Do:

  • If your fish can be transported, consider transporting them with you before you leave.
  • If your fish cannot be transported, cover their pond or aquarium as best you can and follow all evacuation protocols as advised by your local authorities.

12. Severe Injuries

A severe injury usually occurs when a fish gets caught in a filter intake (usually happens to exceptionally weak fish) or is attacked by a predator and survives. In other cases, poisoning from a substance (such as alcohol) can cause severe injuries too.

Signs of Injuries:

  • A visible lesion on your fish (a cut, bite wound)
  • Visible bleeding
  • Missing fins or tail
  • Inappetance
  • Fish is stuck somewhere in the aquarium or pond and can’t wriggle free

How to Confirm:

  • Observing your fish can quickly help you diagnose an injury.

What to Do:

  • Isolate your fish in a quarantine tank and assess them.
  • Contact your veterinarian for a home visit, if possible.
  • If their injury is severe, consider a second opinion from a veterinarian for euthanasia. Euthanasia may be performed by your vet or by you, if needed.
    • Note: do not feed your fish for 2 days before euthanizing them. This ensures that the euthanasia medicine is quickly absorbed and your fish doesn’t suffer throughout the ordeal.
  • Try appropriate treatment options, if possible. Most severe injuries require veterinary input and care.

How to Prevent It:

  • Keeping your fish as safe as possible and in the correct setup minimizes the risk of injury.

13. Infectious Disease Emergencies

Sick goldfish lying in the bottom
Image Credit: mrk3PHOTO, Shutterstock

A few bacterial, viral, parasitic, and protozoal infections can cause the rapid death of pet goldfish. These aren’t the same agents that cause diseases such as fin rot or Ich but rather diseases that manifest as signs of extreme distress.

Signs of Infectious Disease Emergencies:

  • Sudden death
  • Erratic swimming patterns (flashing)
  • Tiny red spots on your fish
  • Your fish’s eye suddenly bulges out or even pops out
  • Your fish suddenly appears extremely bloated with a pinecone appearance (also known as dropsy)
  • Unknown projectile or excretions from your fish that don’t look like poop
  • Gills appearing red
  • Gasping at the surface (piping)

How to Confirm:

  • These severely dangerous, rapidly progressing diseases are best confirmed by a veterinarian.

What to Do:

  • Immediately perform a large water change of around 30–50%.
  • Call your aquatic veterinarian promptly. If they cannot come to you, take your fish to them.
  • Ensure you place each fish in their own container or bag during transport.
  • Bring along spare aquarium water, around 0.3 gallons (1 liter) for your veterinarian to examine.
  • Follow your veterinarian’s advice for treatment.

How to Prevent It:

  • Quarantine any new fish for a period of 4–6 weeks before introducing them to an existing tank.
  • A UV lamp in your aquarium filter can help kill certain dangerous pathogens.

Have an Emergency Kit

As prompt intervention is key to averting a crisis in some situations, it’s handy to keep an emergency kit at your home. This is a collection of supplies, medicine, and other useful items that can help in an emergency.

Check out some important things to have in an emergency kit:
  • A quarantine or hospital aquarium (ensure this has filtration and an air stone)
  • Spare net
  • Extra water test kits
  • Stress medication
  • Commercial nitrifying bacteria
  • Water conditioner
  • Commercial ammonia binders
  • pH modifiers
  • Aquarium salt
  • Your aquatic veterinarian’s number
  • Spare air pumps (preferably portable ones)
  • Spare buckets or transport tanks
  • Spare plastic bags
  • Spare oxygen cylinders

In some unfortunate situations, you might have to make a decision to end your fish’s suffering by humanely euthanizing them.

In such a case, it’s good to have the following:
  • MS-22: This drug is FDA-approved and is readily available in pet stores. It may be sold under one of the following names: tricaine methanesulfonate, “Finquel,” or “Tricaine-S”.
  • Clove Oil

It is best to keep euthanasia products away from the rest of your kit.



Though unfortunate, goldfish emergencies do happen at times. While some circumstances are unavoidable, others can be prevented with proper setups, and prompt intervention. We hope this article helps you better understand what to do in case you ever notice your fish in distress.

Featured Image Credit: M-Production, Shutterstock

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