Behavioral Signs of A Sick Goldfish – The top 5 tell-tale behavior that your goldfish is unwell

In spite of the common misconception that goldfish are really easy to keep, they are in actual fact a very demanding fish.

For instance… goldfish eat and poop a lot, so water quality of their living environment deteriorates very quickly if you do not provide good water filtration and regular maintenance. They can also grow really large, thus requiring a lot of swimming space to be happy and healthy.

Besides that, goldfish have been bred for many generations with their body structures altered into forms that hobbyists find attractive, but in reality are design flaws that expose these breeds to injuries and health risks.

All these are just some of many possible reasons that can get your goldfish sick. When this happens, your goldfish will display some tell-tale behavior that things are not going well, before the sickness manifest into physical signs on the body.

So it is very important to pick up on these behavioral signs of a sick goldfish, so that you can take early actions to make it better,…but do you know what signs to look out for?

Signs of a sick goldfish
I am not feeling well… 🙁

What are the behavioral signs of a sick goldfish?

Remember I mentioned earlier that goldfish eat and poop a lot? Yeah, a healthy goldfish will always be on a lookout for its next meal, unless it is sleeping. In case you are wondering, goldfish do need their beauty sleep too! 😉

A healthy goldfish is very active. It swims around, interacts with its fellow tank mates and sifts through substrates hoping to find something to eat.

A healthy Telescope goldfish sifting through sand

A change in this behavior serves as a warning. Here are the top 5 behavioral signs that your goldfish is telling you “Help me!”.

1. Loss of Appetite

Goldfish embody the phrase “Eat all you can”. Even after you have fed them, they act as if you are starving them, and eager for your next serving.

Goldfish Feeding

So if you see your goldfish showing no interest in food – SOMETHING IS WRONG! If you see your goldfish is losing weight and you did not put it under a strict diet regime – SOMETHING IS WRONG!

2. Clamped Fins

Healthy goldfish have their fins spread out. If your goldfish’s fins are clamped up all of the time, and it is either stagnant, or with little movement but not going anywhere; raise the alert!

This is one of the most obvious early signs of a sick goldfish.

Goldfish Stress
Clamped Fins

3. Constantly Hiding

If you have just introduced the goldfish into the tank, then it is normal for the fish to display this behavior initially. It’s a new environment and it needs time to adapt and to make sure that it’s safe. I am not sure about you, but I tend to hide in the toilet quite often when I start a new job. #shy #introvert

However if your goldfish is constantly hiding even after a week or so being in the tank, then something is off. Try checking whether it is a victim of fish bullying. It does happen you know, due to incompatible tank mates. If that is the case, you may need to isolate the fish (the victim or the bully).



4. Gasping for air at the water surface

Goldfish that keep gasping for air at the surface indicates that they are having a hard time breathing. This can be caused by the lack of oxygen in the water (for example when the water gets too warm), presence of toxic compounds or infected gills.

Goldfish gasping for air

5. Abnormal Swimming

If your goldfish is not swimming, you should be concerned. If your goldfish is swimming in the following manners, you should also be concerned!

a) swimming off balance or upside down – possible cause: swim bladder problem
b) swimming erratically – possible cause: bad water quality
c) swimming and rubbing itself against items in the tank – possible cause: parasites such as ick and anchor worm



What should I do when I see these signs?

These behavioral signs are early indicators that your goldfish is getting sick. At this point, you may not be able to diagnose the actual disease and treat it accordingly.

However when you start taking early actions, you are helping your goldfish to get out of a stressful condition sooner and help boost its immune system. This immune system will be your goldfish’s defence against diseases.

Below are the 3 general mitigation actions that I take when I encounter any of those behavioral signs of a sick goldfish:

1. Check the Water Quality

If most of your fish in the tank are affected, do a water test on your tank. Hmm…come to think of it, I will go a step further and say that even if only one fish is affected, do the water test anyway!

I can tell you that in a lot of cases, the water quality of the fish tank is the culprit. If you do not have a water test kit, you should really get one. I would highly recommend you this: API Freshwater Master Test Kit.

Click here to read my review on it.Fish Tank Water Testing KitIf the test results show that there is ammonia or nitrite in the water, immediately do a 25%-50% of water change and repeat this every 2-3 days until you see their concentration goes down. Ammonia and nitrite are highly toxic to fishes!

2. Isolate the sick goldfish

As a precaution, isolate the sick goldfish from the rest of the tank. This is to prevent the sickness from spreading to the rest of the healthy tank occupants. Take the sick goldfish out and put it in a quarantine tank that is already cycled.

If that quarantine tank is not cycled, then be prepared to do regular water test and water changes so that the level of ammonia and nitrite can be brought way down.



3. Aquarium Salt treatment

I add and dissolve 1 tablespoon of aquarium salt for every 5 gallons of water into the tank that my sick goldfish is in. Aquarium salt is a source of electrolytes for the fish, encourages slime coat production on the fish and has the ability to weaken pathogens.

However please note that not all fishes can tolerate aquarium salt treatment. If you intend to use it with other fishes, please do your research to ensure their tolerance level.

Read more about the benefits of using aquarium salt with your goldfish here.


So what are your thoughts on this? Have you encountered any other behavioral signs of a sick goldfish? What do you do when you see these signs? Please share and leave them in the comment section below.

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