Dropsy fish disease is much more common in freshwater fishes than in marine fishes. It is a condition where the fish looks bloated. Most aquarists are stumped by what causes Dropsy.

Therefore, in this article, you will learn what causes swollen fish drops, what you can do to prevent it, treatment, and all other necessary knowledge needed to manage it.


Dropsy was an old medical term for a disease that is now more commonly referred to as edema or ascites. The phrase comes from the Middle English word dropesie, the Old French word, and the Greek word hydrops, a derivation of the word hydro, which means water.

Dropsy can be caused by a variety of factors, including:

  • Organ failure
  • Incorrect water chemistry
  • Poor aquarium hygiene
  • Secondary disease affecting the gills, heart, kidneys, liver

To address the swelling, you first have to address the preexisting condition that gave rise to the visible symptom. One may ask, are all types of fish susceptible to this?

Types of Fish Affected

Dropsy isn’t restricted to a single type of fish. This infection can affect any form of fish kept in an aquarium, but goldfish seem to be the most commonly affected. However, you should note that fish with a weak immune system are more susceptible to this disease.

Tackle one problem and another comes up; how do I know a dropsy fish when I see it?

Symptoms of Dropsy in Fish

We will divide the symptoms of dropsy in fish into physiological and behavioral changes to help us understand them better.

– Physiological changes

Ascitic fluid builds up, putting pressure on the abdominal wall. This is the cause of the bloated belly in fish. As the condition worsens and more fluid accumulates, scaled fishes will display protrusions of these scales or plates, giving the fish a hideous “pinecone” look.

Inflated eyes, pale gills, swollen anus with a bloody coloration, pale urine, a bent tail, clamped fins are other visible manifestations. Most times, at this stage, it is a little too late for something to be done. This is because the underlying disease must have gone on for a long while.

– Behavioral changes

Lethargic movement (when the fish only hover at the top of the tank instead of swimming), loss of appetite, and so on, are easy to spot if the fish exhibit them. Proper diagnostic tests and examinations should be carried out to ascertain the reason for the changes. This could help avert a more severe crisis or even death.

Looking at what the norm should be will help us understand the abnormal changes.

Normal Fish Physiology

We must first examine fish anatomy and its physiology to understand what causes dropsy and how it can be handled and avoided.

So grab your notebooks because we’re returning to the basics.

– Osmoregulation

Ions such as Na+ are dissolved in the tissue fluids of these fish. These, together with plasma proteins, give the fish a higher osmotic differential than the freshwater they swim. As a result, osmosis draws water molecules into the fish’s body through porous surfaces and can lose electrolytes through diffusion.

The skin is thickened and coated in scales or bony plates. This makes the body surface impermeable. Two organs, however, must maintain water permeability: the gills for gas exchange and nitrogenous waste excretion, and the gut, for absorption of nutrients.

Adapting to the constant salt loss and water influx through the gills and stomach is critical for freshwater fish.

Now here comes another confusion, are all bloating a case of fish dropsy?

Can Fish Bloat for Some Other Reason?

Yes. Not all fish bloat is a case of fish dropsy, so care is needed to avoid giving a wrong diagnosis. Internal tumors or the fish being a gravid (full of eggs/fry) female are other causes of abdominal distension.

– Tumorous Growths

Tumorous growths rarely cause asymmetrical distension of the abdomen; instead, a protrusion to one side or biased to the front or back of the fish will be visible, with scales protruding only rarely.

– Gravid Female

Gravid females may have round bellies, with protruding scales on rare occasions. But no other disease symptoms, including loss of color, appetite, fin erosion, or respiratory distress, will also be found.

What Causes Dropsy?

A whole number of reasons can cause a fish to bloat. Some are infections from viruses, bacteria, and poor aquarium hygiene.

Remember that once the gills, kidney, and liver integrity are disturbed, the fish is very likely to bloat.

– Incorrect Water Chemistry

Any fish disease investigation starts with a comprehensive water quality assessment. Cloudy water may be caused by a high concentration of dissolved constituents such as phosphates, silicates, or heavy metals. This, along with an increase in the nitrate levels, will encourage the growth of harmful pathogens.

– Stress

This could be for several reasons. It could be from the transport of the fishes. Also could be from it’s an attempt to adapt to a new environment. In most cases, a single or brief exposure to stress would not impair the fish’s ability to combat infection. Prolonged exposure to stress affects the fish’s immune system. Multiple stress factors must occur in rapid succession for this to be a factor.

– Poor Nourishment

To live a healthy life, fish need all of the essential nutrient categories. Unfortunately, many fish keepers do not read or appreciate the nutritional quality of fish food container labels. As a result, they may not be supplying nutritionally adequate food. It’s essential to understand what the information on the label means and whether the food contains the nutrients your fish needs to remain healthy.

– Temperature Changes

Since they are poikilothermic marine vertebrates, the water temperature significantly impacts their metabolism and immunity. The immune response of fish is suppressed when the water temperature drops.

The majority of pond fish diseases strike during the spring and fall when temperature fluctuations are worse. For every 10 degrees Celsius increase in temperature, biologic activity doubles. If the temperature rises and the amount of dissolved oxygen that the water can retain decreases, the toxicity of ammonia rises, resulting in hypoxia.

– Tank Mates

The partner species housed in one tank play a role in the fish’s comfortability and care. If the fish is intimidated by its tank mates, it may not feed properly. Aggressive tank mates can obstruct the structural integrity of the fish, thereby letting in opportunistic pathogens.

– Proper Diagnosis

Once you ascertain the problem, the job is half done. All you need is to implement the solution, and all is good with the world.

A positive bacteriologic culture of infected organs or lesions is the best approach for diagnosing this disease in fish. Confirmation of the characteristic lesions with histopathology clears all doubt.

Start with the basic questions first. Take into account the environment’s recent past. Have you added any new plant, fish, or invertebrates? Have you recently treated fish or had some critical hardware fail? Answers to these will help inform on the following action to be taken.

How to Treat a Dropsy Fish

Treating dropsy is easier said than done. Most times, when the physical manifestations of fish dropsy occur, it’s a little too late for any treatment to be effective.

But, if the symptom is discovered early enough, the first cause of action should be to tackle causative agents. It could be any of the factors listed above. If any of the abiotic conditions is not met correctly, it should be addressed first.

– Maintaining Good Water Quality

Fortunately, maintaining water quality is simple with good hygiene. This involves regularly cleaning the water filter, using the correct aquarium cleaning agents, and generally ensuring that your aquarium maintains a balanced atmosphere for the fish’s wellbeing.

Tetra’s Test 6in1 will include a simple overview of water parameters, along with its free water testing app. Avoid much exposure to sunlight; it limits the growth of algae in the aquarium, which checks the level of nitrates in the tank.

– Temperature Levels

Maintain the temperature in the fish tank between 78 and 80 degrees Fahrenheit. It’s worth noting, however, that the number varies depending on the breed. Ideally, you should find out what temperature your fish prefers and set your aquarium to that temperature. This way, you can be sure that the atmosphere is suitable for your pet.

– Good Compatible Tank Mates

Do thorough research to establish compatible tank mates for the pets. Compatible tank mates ensure that your fish is comfortable and feels at home.

– Disinfect the Tank

Use a 0.2 percent solution of Acriflavine or Monacrin at a rate of 1ml per liter to disinfect your fish tank. Don’t continue if your fish aren’t responding well.

After ensuring that the fish tank’s abiotic conditions are met, the next step is to take care of the bloated fish belly.

– Euthanization

The infection that causes dropsy is a bit difficult to treat. Some experts suggest that all infected fish be euthanized to prevent the disease from spreading to healthy fish.

What to Do if Only One Fish Is Affected

If only one fish is infected, it is important to isolate it; keep in mind that various pathogens can cause multiple organ failures. The affected fish is almost certainly a pathogen reservoir. Isolation tanks must be kept separate from the main stock and equipped with dedicated filtration, nets, and siphons, among other things.

In the hospital tank, add one teaspoon of salt per gallon of water. You can use sodium chloride in place of Epsom salt.

If the ascites are caused by kidney failure, salting to 3 g/l reduces the osmotic influx of water into the fish by one-third. Thus reducing the load on the struggling kidney and likely promoting a self-cure. Salting will have little impact if the ascites are caused by liver or splenic injury.

  • Provide your fish with high-quality foods.
  • Antibiotics and other dropsy medication, should be provided to the fish, either in the food or in the water. If you intend to add it to the food, it’s best to starve the fish for a little while. Starvation forces it to consume the food mixed with antibiotics.
  • Every day, check the water in the hospital tank to ensure it’s safe for the fish.
  • If the fish is still very bloated, any operation would almost certainly be void because the fluid’s pressure has caused too much internal damage.


  • Dropsy fish is a disease that causes the abdomen of the fish to bloat
  • It occurs as a result of improper abiotic conditions
  • It can be prevented with proper diet and water conditions

Poor abiotic conditions compromise the immunity of fish against opportunistic pathogens.

Isolation of the infected fish helps, along with a proper examination of other fishes for the symptom. However, we still advise that prevention is better than cure when it comes to dropsy disease.

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