Illness and Disease Fish Tank Guides

Dropsy in fish – Fish Illness


A guide to Dropsy in fish.


Dropsy in fish is seen very frequently in the home aquarium. The classic signs of a swollen belly and ‘pine coning’ scales are often pretty unmistakable. Dropsy is quite a severe illness in fish and it has a very high mortality rate. It is caused by the fish’ body swelling with fluid, this means that the body is stretched causing scales to stick out in that pine cone effect. It also means that there is less space in the fish’ body for its own organs, this often causes the fish to bend out of shape and means that its vital organs shut down, ultimately leading to the death of the fish.

Dropsy is caused by a bacteria that is common in aquariums, it is called Aeromonas bacteria. The good news is that despite the presence of this bacteria in your aquarium, a healthy fish’ immune system will fight it off and it won’t be able to harm the fish.

Problems occur when a fish’ immune system is compromised, this can be caused by stress, bullying or another infection. Once the fish’ immune system is weakened, it allows the Aeromonas bacteria to do its damage.


Signs of dropsy in fish

Dropsy often presents some fairly obvious symptoms. The fish swelling is usually pretty noticeable as it fills with fluid, this leads to the ‘pine coning’ scales, where the scales appear to point out instead of being flush against the fish’ body. Scales pointing out is usually a sign that the dropsy has become fairly advanced and the fish has swelled to capacity.

Other symptoms of dropsy include:

Fish being lethargic.

Loss of appetite.

Hanging at the top or bottom of the aquarium, instead of swimming normally.

Legions/Ulcers on the skin.

Pale colouration and pale gills.

Bulging eyes.

Pale and stringy poop.

Curved spine.

Redness in the fins and/or skin.

dropsy in fish


Most if not all of these symptoms can also be caused by other infections/issues, so if your fish isn’t noticeably swollen then it can be difficult to diagnose dropsy. Swelling is a very common symptom though, so if you are not sure if your fish has dropsy or not, if it does then it is likely that it will soon swell up, then you can be pretty confident in your diagnosis.


Treating dropsy in fish

Treatment of dropsy can be very challenging. Once this infection takes hold it can be very difficult to reverse, it is not helped that it is often caused due to a previous, additional infection that may also be attacking the fish and weakening the immune system further.

Many aquarists will advise you to euthanise a fish with dropsy to prevent the spread of infection to other healthy fish, particularly if it has advanced to the stage of scales poking out of the fish.

There are a few things to try when attempting to treat dropsy, but please be warned that it has a very high mortality rate and success in treating it does not happen frequently. Here are a few things to try if you have a fish suffering with dropsy:

  1. Move the affected fish to a separate hospital tank – this helps to prevent the spread of the infection to other fish.
  2. Add aquarium salt to the water – Ordinary table salt can be used too at 1 teaspoon per 4.5 litres of water.
  3. Treat with antibiotics – these can be purchased in most pet stores for use with fish, some will specifically be aimed at fish suffering with dropsy.
  4. Feed high-quality food.
  5. Keep water quality perfect – any drop in water quality will weaken the fish’ immune system so it is important to keep the water immaculate to give the fish the best fighting chance. Regular water tests are a must.
  6. Think positive thoughts – as I said, dropsy in fish is very difficult to cure, so you will need to be positive and rely on a little luck to help you through.



Preventing dropsy in fish

Dropsy is very common in the aquarium and the bacteria that causes it is almost always present. Preventing the bacteria from infecting your fish is vital, as once it takes effect it can be very difficult to stop and can, if left unchecked, wipe out an entire tank in a fairly short space of time.

Dropsy is highly lethal to fish so it is important to do your best to prevent it from infecting your fish. Here are some steps you can take to help prevent your fish from being infected by dropsy, though most are good practice anyway:

  1. Have a quarantine tank – Stressed or sick fish are prone to dropsy, so new fish should be quarantined for at least 2 weeks before being added to your main aquarium. This allows you to be sure that they do not have an existing illness that could spread to your existing fish. Transit is often stressful for fish and can mean that they already have a weakened immune system when they arrive home with you.
  2. Maintenance – Maintenance is important for a healthy tank in general and will help to prevent any infection or illness affecting your fish.
  3. Water quality – Kepp the water quality high, performing regular water changes and vacuuming the gravel/substrate will help to keep your tank happy and healthy.
  4. Maintain your filter correctly – Filters require routine maintenance to keep your water clear and detoxified from waste.
  5. Don’t overstock.
  6. Feed a high-quality varied diet – This ensures that your fish receive all the vitamins and nourishment that they need to keep their immune system strong and healthy, meaning they are less susceptible to any affliction.



Dropsy in fish – Final thoughts

Dropsy is very difficult to cure, so if it has occurred in your aquarium I wish you the best of luck in fighting it. The steps above may help but, unfortunately, there is no guarantee that your poor fishy(s) will survive. If your fish is in the advanced stages of dropsy, then I may have to agree with others that euthanasia is the best option, not only to prevent the spread of the infection but also to relieve the fish from the high level of pain that it is likely in.

Prevention as always is better than the cure, so keeping a happy healthy aquarium is always the best way to play the game.

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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