Goldfish Fin Rot: Identify The Symptoms & Cure Immediately!

goldfish fin rot
Japanese Fighting Fish is reader-supported. When you purchase through one of our links we may earn an affiliate commission (at no extra cost to you).

Last Updated: February 27, 2023 by Flora Gibbins

Goldfish are a hardy species, a member of the carp family. They prefer static to slow-moving waters. No wonder they can survive in a bowl, aquarium, or pond. Generally, people assume goldfish are aquatic drones without emotion and pain. They are tenacious, but let’s not stretch it too far.

Let’s see…

Goldfish experience trauma and stress. In a non-conducive environment, they suffer from fin rot at a higher rate than other tank mates.

Let’s unpack why and how goldfish fins die.

How to Spot Goldfish Fin Rot

First, it’s salient to point out that fin rot in goldfish is primarily a manifestation of detrimental environmental factors rather than a disease. That’s why it’s equally easily preventable.

goldfish with tail fin rot image

Look out for:

  • Darkened, rugged fin edges
  • Seemingly torn or frayed fins
  • Black or white patches on the tail, fin, or sometimes the whole body
  • Redness or inflammation at the base of fins and tail
  • The infected area completely falling off
  • Lethargy
  • Loss of appetite

When you notice such signs, the first step is to examine the body for more issues requiring intervention. Next, determine the source of the bacterial infection.

The discoloration in the fins may seem white, crimson, or even black, depending on the natural color of the goldfish. The fin tips become ragged and uneven as dead flesh rot and flake away. The bacteria then proceeds to attack the internal organs, which will now destroy the fish’s immune system, potentially causing death.

What Causes Goldfish Fin Rot?

1. Waste Products

pair of goldfish in a fish tank

The waste products in the goldfish tank raise ammonia levels. I can’t emphasize the need to maintain the water quality enough.

Keep changing the water and clearing the gravel at the bottom of the tank to remove the fish food and other residues. If the water is appearing milky white and the ammonia stench is repugnant, it indicates poor water quality.

2. Environmental Factors

Goldfish fin rot is the initial pointer to environmental problems within the tank. The fins are prone to damage when ammonia builds up. An intoxicated environment is always habitable to harmful bacteria, which burn away the fins.

Goldfish are hyperactive and may go for days without eating.
goldfish in the bottom tank

So it’s understandable that you may not immediately notice their appetite loss.

Normally, they flash their colorful flowing fins to express happiness and good health. Simply examine their fins to see if they are open or closed. If they are closed, that is a problem. Your aquarium fish may be stressed, or it could be some other issue. All the same, clamped fins are never a good sign.

Goldfish survive best within a neutral pH range of 7-8. When the pH drops, the water becomes acidic, meaning your goldies are now susceptible to a secondary fungal infection or other common diseases.

Your senses are arguably the most critical monitor! The severity of the pungent “stench” that may float over the water’s surface is a big clue that a water change and treatment are due.

3. Overpopulation

oranda goldfish in aquarium

Overcrowding rolls back to high-stress levels, one of the leading causes of fin rot. The governing rule is to stock one-inch fish for every gallon of water. For example, if yours is a 10-gallon tank, you can stock ten 1-inch fish, 5-2 inches fish, and 2-5 inches fish. Do you get the drift?

This guideline is a rough estimate, but if you go beyond it, you’ll have courted trouble.
Factoid: One disease that most goldfish owners make them scratch their heads is discoloration. Learn how this happens and what steps to take in preventing this from happening. Read our article here — Why Is My Goldfish Turning Black: We Check 6 Possible Claims.

4. Aggressive Tank Mates

aggressive goldfish mate in a tank

If you decide to have other fish species in the tank, you have to consider whether they’re neighborly or not. Having docile and aggressive fish in one tank means subjecting the timid ones to bullying. Once their stress levels hit rocket high, you’ll have lost your pet.

5. Poor Diet

If you’re not going to take care of goldfish dietary needs, please leave them at the pet store. You’re better off collecting stamps or engaging in any other hobby. I always tell anyone who cares to listen that if you can’t take care of any pet as you would your child, please don’t take it home.

Growing the Fins after Goldfish Fin Rot

beautiful bright goldfish in aquarium

This is your starting point in designing your treatment plan. Prevention and treatment of goldfish fin rot are ‘Do It Yourself Activities.’

Treating your goldfish fins starts with the assessment process to determine what is wrong and how to apply the necessary remedies.

It is challenging to identify goldfish fin rot without complete information on water analysis results, background, aquarium size, tank mates, and so on, but here are a few things to keep in mind.

When you observe the scorching of the fins, visit the pet store for a water kit to check ammonia and pH levels. Ammonia has a drastic effect on the goldfish. You also need to segregate the sick fish in a quarantine tank

Relax! Goldfish fin rot is a reversible infection.
Fun Fact: Don’t wait for your golden buddy to acquire this illness. There are ways to prevent this disease from happening and save you (and yourself) from a heap of impractical expense and stress! Read our article about this here — Goldfish Care: Tips & Strategies To Keep You Goldie Healthy.

Managing and Preventing Goldfish Fin Rot

If the salt level in your aquarium exceeds one ppm (parts per million) on a conventional test kit, start water treatment right away. A 60 percent water change, along with reducing the pH of the water, will bring rapid relief (add water with the same temperature as that in the fish tank).

Several water changes in a short time are necessary to reduce the concentration of aquarium salts to less than one ppm.

I highly recommend you go to the pet store, get a water test kit, and check the pH level and ammonia level because if it is too out of range, it will drastically affect the healthy fish.

Interestingly, goldfish hardly change color more than once in their life; beyond the first color transition after birth, they never change color again unless environmental factors influence their physical characteristics.

The affected fin makes swimming challenging. Besides improving water standards during the early stages, anti-fungal treatment with a broad spectrum of appropriate antibiotics such as Melafix may do the trick. It is an effective treatment for fin rot and other symptoms of poor health.

The water changes are effective as primary management of goldfish fin rot. Try reintroducing the affected fish into the tank once the fin is healed completely.

The five most important factors to check when accessing the cause of fin rot are;

  • Aquarium water conditions
  • The filter setup
  • Environmental factors(temperature)
  • Type of tank mates
  • Physical characteristics(feeding behavior and fin looks)

Do It Yourself, No Vets!

As fish keepers, note the behavior changes as they will be critical when you have to do the primary management of the goldfish fin rot.

You’ll have to restore the water balance for the fish to recuperate. Gravel cleaning and timely water changing are the best practices for preventing fin rot.

Ammonia poisoning is quite different from fin rot. The former will have distinct symptoms which affect the gills and other internal organs, such as loss of appetite, red gills, lethargy, and gasping for air on the water surface.

Remember, your goldfish may survive in water with low oxygen levels, but adequate aeration is vital for the internal organs to function as required.

You might want to keep an air-stone in an aquarium to assist with aeration and extend the time between good housekeeping. If you ignore essential maintenance, the sheer “waste burden” of goldfish will eventually overpower the finest aeration, deplete the oxygen, and increase the rate of fin rot.

An important hack: your goldfish will not tolerate fast water current.

When using power filtration, position the discharge to minimize excess currents without altering the circulation.

If the fin rot symptoms persist, call your vet for professional advice.

Treatment Checklist

As part of the treatment plan, check on these probing questions. They may help identify the root cause of the problem as if you were the vet.

Did you prepare the water before putting it in the aquarium during the routine water change?

If you fail to prepare the water properly, the fish may experience traumatic episodes or suffer from aquarium salts in the tank water.

If you changed the water, did you do a 100% water change?

Tap water is high in nitrates. While most water companies keep the levels low, periodically wash the water tank to reduce the residue that may cause the growth of gram-negative bacteria.

Removing 100% of the water from the aquarium removes the much-needed good bacteria. You shouldn’t do an entire water overhaul frequently because growing back the good bacteria takes weeks. A regular 25% water change is enough to solve the poor water quality situation.

Have you recently added anything else to the aquarium? (plants/ other fish/or decorations)

Introducing new objects runs the risk of causing injuries leading to fin rot. Ensure you only place objects with smooth edges.

Frequently Asked Questions

Is goldfish fin rot contagious?

Unfortunately, it is. The causative agent, gram-negative bacteria, has a slime layer on the outer membrane, making it resilient and facilitating its spread.

The enclosed nature of an aquarium doesn’t make the situation any better. No matter how large it is, the water is still retained within, making it easy to spread contagion. By the time the water goes through the filtration system, it will have been infected anyway.

You could consider putting the affected fish in a quarantine tank to mitigate the spread.

What is the simplest procedure to prevent goldfish fin rot?

The simplest way to prevent and treat fin rot is to check the environmental factors such as pH and temperature using the aquarium water test kit. Changing 25%-30% of the water goes a long way in keeping the fish healthy.

Does aquarium salt heal goldfish fin rot?

Yes, non-iodized salt(common salt) and rock salt can cure fin rot. It is crucial to ensure that it is pure sodium chloride without additives. Also, using salt is only effective in less severe cases.

How do you tell if your goldfish is recovering from fin rot?

A white tissue around the affected fins indicates healing, while a ragged red edge means persistent infection.


More often than not, fish rot is always a water parameters issue. Keeping the tank clean will save you from unnecessary ailments. Regularly change the percentage of the water, use an effective filter, keep the population acceptable, and use antibiotics for primary and secondary fin rot.

Goldfish are “goldies” in their name for a reason. You have no choice but to treat them like the precious stone they’re named after.

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *