Dropsy in Aquarium Fish – Treatment, Cure and Prevention

Dropsy Goldfish

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Dropsy is a catch-all term used when fish in our aquariums swell up. Dropsy is essentially swelling of the soft tissues in the body cavity due to the accumulation of fluids in the body.

Dropsy is usually caused by the presents of Aeromonas bacteria, a bacteria which usually only affects fish that already have a compromised immune system. Dropsy affects almost all species of fish in the hobby

What is Dropsy?

Dropsy, a term that is only really used in fish medicine these days (although it used to be more widely used in general medicine), is used to describe fish that have very swollen abdomens. These swellings can be so extreme that a fish’s belly can actually hang down beneath its body.

Dropsy is also occasionally referred to as bloat, although it is not the same as Malawi Bloat.

The bacteria that causes Dropsy is ever-present in our aquariums, hence it is a problem that any fish can suffer from. However, healthy fish can usually fight off the bacteria and don’t tend to suffer from Dropsy.

The Aeromonas bacteria take advantage of fish whose immune system is compromised, either because that fish is already sick, or because the fish is under stress for some reason.

It is possible to have a tank full of fish, all of whom are living in the same conditions, yet only one or two fish suffer from Dropsy.

What are the Causes of Dropsy?

Dropsy is caused by Aeromonas bacteria. These bacteria are ever-present in our aquariums, yet the majority of healthy fish simply fight them off and never suffer from Dropsy.

Aeromonas bacteria are referred to as gram-negative bacteria because it does not show up in laboratory tests known as the Gram Stain tests. Gram Stain tests are a method of identifying bacteria species.

Healthy fish successfully manage to fight off this bacteria, however, fish that have an already compromised immune system, perhaps because they are sick or stressed, are attacked by the bacteria.

Stress factors that can affect fish include;

  • Poor water quality
  • High or low water temperatures
  • High levels of ammonia, nitrite, or nitrate
  • Poor quality diet
  • Stress due to transportation
  • Bullying tank mates
  • Environmental factors (such as loud noises or bright light outside the tank)

One or more of these factors can be enough to stress fish to the point they begin to suffer from Dropsy.

What are the Symptoms of Dropsy?

The main symptom of Dropsy, or at least the one people tend to notice first, is the very swollen belly fish get. Often the swelling is so server the fish’s scales actually start to protrude outwards. This effect is often referred to as giving the fish a pinecone-like appearance.

Other symptoms of Dropsy include;

  • Swollen Belly
  • Scales sticking out from the body
  • Pale gills
  • Stringy white poop
  • Clamped fins
  • Bulging eyes
  • Loss of appetite
  • Loss of energy
  • Curved spine

Often, when a fish is suffering from Dropsy the symptoms start off mildly, then become more server as the disease progresses. Fish in the early stages of Dropsy may not be showing pale gills, but as the internal organs become affected, anemia can show in the gills and the mouth.

Occasionally, fish suffering from Dropsy may find the internal swelling moves their swim bladder (the organ fish use to stay upright in the water) meaning the fish struggles to stay buoyant and may end up floating upside down.

How to Treat Dropsy?

Dropsy is not a disease that is easy to treat. I know many professional fish breeders that will simply euthanize any fish showing symptoms of Dropsy. I will be honest, the outlook for any fish with Dropsy is not good.

In my experience, providing diagnosis is made early, and treatment starts promptly, fish can be cured of Dropsy.

When treating a fish for Dropsy, I recommend following this procedure below;

  • Remove the sick fish or fish’s from the main tank and place them in a hospital tank (a basic tank with no substrate or decoration, just a heater, and a filter).
  • Treat the water with an appropriate dose of an antibacterial medication like KanaPlex from Seachem.
  • Follow the treatment directions on the medication carefully
  • Carry out regular water changes to prevent a build-up of medication
  • Feed fish good quality foods, especially natural laxatives such as live or frozen Brine Shrimp and Daphnia

Treating Dropsy with Salt

There are many who recommend using salt as a treatment for Dropsy, even in freshwater fish. Salt has excellent antibacterial and antifungal properties and is a great, natural alternative to traditional medications.

If you choose to treat your fish with salt, place the fish into the hospital tank as per the instructions above. Add approximately 1 teaspoon of aquarium salt for every gallon (3.75 liters) of water.

The theory behind using salt as a treatment is the excess fluid in the fish will be drawn out of the fish into the aquarium water, which has a higher salinity than the fish, via osmosis.

Using salt as a treatment can be effective, but it can also be hard on a fish. If you are using this method of treatment, remember to carry out regular partial water changes to keep nitrate levels low, add salt to the new, replacement water only, and feed the fish high-quality food to give it the best chance of surviving the Dropsy.

After a week or two, if the fish appears to have returned back to normal size, it can be returned to the main display aquarium.


How to Prevent Dropsy

As with any pest or disease, prevention is better than cure. With Dropsy, we know the main bacteria that causes the problem is always present in our aquariums, so to prevent it we need to keep our fish in tip-top health at all times, reducing stress whenever possible.

The best way to keep fish healthy and stress-free is to keep the water quality as high as possible. The best way to do that is as follows;

  • Carry out regular maintenance on the aquarium filter to keep it running at optimum performance
  • Feed your fish a high-quality diet. Cheap food has fillers that offer the fish no nutritional value.
  • Feed the fish little and often rather than one large meal a day. It is better for the fish and better for your aquarium water
  • Carry out regular partial water changes, changing between 10% and 25% of the water each week
  • Vacuum the aquarium substrate on a regular basis to help keep nitrates low
  • Test your water on a regular basis using a good quality test kit (I like to use the API Master Test Kit)

In Conclusion

Dropsy can be very hard to treat and has a high mortality rate. There is a good chance, even with your best efforts, that a fish suffering from Dropsy will die.

To give your fish the best chance of NOT developing Dropsy, keep their aquarium water in the best condition you can, and routinely test your water to make sure you don’t have a build-up of ammonia, nitrite, or nitrate as these are often the 3 biggest causes of stress for our aquarium fish.

About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James

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