Dropsy is one of the most dreaded conditions in the aquarium industry. Dropsy causes an excess of fluid to build up in the organs and tissues in the fish’s abdominal cavity. The condition is challenging to treat and likely excruciating.
Dropsy is incredibly fatal — nearly all fish that develop dropsy die because of it.
Almost all aquarium fish have the potential to develop dropsy. Some fish are more prone to the disease, like goldfish.
The most common symptoms of dropsy are swollen abdomens and “pineconing” scales.
Dropsy shares many other symptoms with other illnesses. These shared symptoms often cause dropsy to go misdiagnosed.
For example, dropsy is often confused for bloat or swim bladder disorder. All three disorders cause abdominal swelling.
Dropsy is a symptom, not a disease. Once a fish develops dropsy, it has been dealing with an underlying condition for far too long.
Fish with bacterial, viral, and parasitic infections are prone to dropsy.
Those with liver or kidney troubles tend to develop dropsy.
Dropsy can also develop because of overeating or a nutritional deficiency.
The most common cause of dropsy is the bacteria Aeromonas. Aeromonas are always in aquarium water — healthy fish can fight off the bacteria. Once a fish becomes compromised, the Aeromonas steps in and causes the fish to become sick.
Dropsy is not technically contagious. Fish are more likely to develop it if their tank mate(s) already has it.
It’s tough to cure fish with dropsy. Treatment is possible, especially when caught early.
Aquarists should move the fish to a hospital tank. Keep the water clean and warm, feed nutritious foods, and use antibiotics.
It’s best to prevent dropsy before it occurs since it’s so difficult to treat. Keep the water clean and healthy and feed fish nutritious foods to avoid dropsy.
Euthanasia may be necessary if treatment fails. A fish not responding to treatment is likely in lots of pain; ending their suffering is kinder. The best way to euthanize a fish is by using clove oil.
The Symptoms Of Dropsy
Dropsy is not a disease; it is a set of symptoms resulting from a progressing infection. The condition targets internal organs — particularly the liver and kidneys.
The most recognizable symptom of dropsy is abdominal swelling. The fish’s body absorbs more water than it can handle. The excess fluid causes the organs and tissues within the abdominal cavity to swell.
The fish’s kidneys cannot handle the amount of water coming into the body. Rather than the body excreting the excess fluid, it accumulates in the tissues and organs.
Early Symptoms
The early symptoms of dropsy are similar to many other diseases. The similarities often cause dropsy to be misdiagnosed.
By the time uniquely dropsy-related symptoms crop up, the fish is unlikely to recover.
For fish to be most likely to survive, aquarists should catch the disease as early as possible. The longer the condition progresses, the more unlikely the fish is to survive.
Early signs of dropsy include the following:
- Abdominal swelling
- Red wounds & ulcers on the body and fins
- Decreased appetite
- Loss of color: due to anemia
- Lethargy
- Loss of balance (e.g., lying on their side or abnormal swimming)
- Pale, stringy feces
- Fin clamping
- Hiding
Progressing Symptoms
As the disease progresses, fish may experience some of these symptoms:
- Watery, bulging eyes
- Red & swollen infected anus
- Protruding scales*
- Subcutaneous hemorrhaging
- Abnormal curving of the spine
* Besides a swelling abdomen, the key symptom of severe dropsy is protruding scales. A fish that has protruding scales is known to be “pineconing.” The scales stick from the side of the fish’s body in a way that resembles a pine cone when viewed from above. Once a fish begins pineconing, it’s almost impossible to save them.
Dropsy is so difficult to diagnose because the symptoms vary a lot from fish to fish. Some fish show many of the above symptoms, while others hardly show any.
Most show the classic “swelling” and “pineconing” symptoms, though some don’t.
Dropsy VS Bloat Or Swim Bladder Disorder
Dropsy, bloat, and swim bladder disorders often look similar in the early stages. They all cause abdominal swelling.
Swim bladder disorder and bloat are more common and treatable than dropsy.
Bloat is usually a symptom of constipation. Bloat can eventually lead to swim bladder disorder. Constipation is typically the result of overeating or poor nutrition.
Swim bladder disorder causes buoyancy issues in fish and makes it difficult for them to swim.
Fish can die from untreated swim bladder disorder or bloat, though it’s uncommon. Both conditions are highly treatable. As long as the aquarist treats the fish, they have a high survival rate.
What Causes Dropsy?
Researchers know little about dropsy or the exact causes of the disease. What we know is that dropsy is a bacterial disease caused by the Aeromonas bacteria.
Dropsy most often occurs due to poor water quality. It can also occur due to poor nutrition or because the fish’s body absorbs too much water.
Dropsy is a terrible condition that usually occurs when a fish has been suffering for a long time. It rarely shows up due to a short-term stressor or illness.
Bacteria
The bacteria (Aeromonas) that cause dropsy are present in every aquarium. The bacteria only affect fish with poor immune symptoms.
Fish living in poor conditions have lowered immunity and are likelier to become sick.
Poor Water Quality
Poor water quality can mean several different things. It usually means an ammonia or nitrite spike.
These spikes occur because of insufficient cleaning or overfeeding. Fish food and/or waste accumulates in the aquarium, breaking down into toxins.
Poor water quality can also mean rapid temperature fluctuations. These are highly stressful for fish and can cause them to go into shock.
Age
A fish becomes more susceptible to dropsy the older it gets.
Elderly fish are more likely to develop viral, bacterial, or parasitic infections. They are also more likely to experience kidney failure, which can cause dropsy.
Unhealthy Foods & Overfeeding
Foods lacking nutrients can make fish more susceptible to dropsy.
Overfeeding fish or only feeding them dry foods can also make them more susceptible.
Bullying & Stress
Bullied fish are more susceptible to illness. They deal with constant stress, which lowers their immune systems. They can also develop injuries from bullying, which leaves the fish open to infection.
How To Treat Dropsy
Researchers don’t know much about dropsy, which is why treatment is rarely effective.
The best treatment is the one that is targeting the cause of the dropsy.
For example, clean the water if the water quality is suffering. Provide foods high in nutrition if the fish developed dropsy due to a poor diet.
Unfortunately, treating dropsy based on the cause is difficult. It can be challenging to pinpoint what is causing it.
Move Fish To A Quarantine Tank
Quarantining a sick fish is the best thing for the fish. Treating ill fish in a small, more controlled environment is more manageable than in a large tank.
Hospital tanks usually have bare bottoms with few decorations. They shouldn’t be completely empty, as a few decorations make the fish feel more secure.
Use A Filter, Heater, & Airstone
Hospital tanks must contain a small filter and heater. They help create the ideal healing environment for the fish.
Placing a small airstone in the tank is ideal since it oxygenates the water. Ensure the current from the airstone is not too strong for the fish.
Cleaning
It’s easier to clean a quarantine tank than a display tank because they are smaller. Most quarantine tanks need daily water changes during treatment.
The Water Level
Keep the water level low in the quarantine tank. A shallow tank makes it easier for the fish to swim to the surface to eat or get air.
Medicating
It’s better to medicate isolated sick fish in a quarantine tank than the display tank.
Healthy fish should stay in the main tank and not be exposed to the medication. Medicating healthy fish can cause them stress. In some cases, it can make them more resistant to medication if they need it in the future.
NEVER pour water from the hospital tank back into the display tank after treatment.
Perform a significant water change (30-50%) on the display tank. Doing so makes the environment healthier for the remaining fish.
Watch those fish closely for any signs of illness or discomfort.
Increase The Water Temperature
Using a heater, slowly increase the water temperature to help the fish fight dropsy.
Warmer temperatures help draw excess fluid from the fish’s body to reduce swelling.
The water temperature should generally be between 78-86°F (26-30°C).
The exact temperature range depends on the species. Always research what temperatures a species can handle before raising the temperature.
Only raise the temperature by 1-2 degrees a day to prevent shocking the fish.
Feed Fish High-Quality Food
Flakes and pellets are staple foods for most aquarium species, though not all dry foods are equal. Always research the best brands to ensure the fish get the best quality food.
Look at the ingredients list. Pick brands that list healthy foods as their top ingredients.
Although pellets and flakes are good staples, they shouldn’t be a fish’s primary food source.
Add variety to their diet. Supplement them with freeze-dried, frozen, and live foods.
Ensure these foods are also high-quality and nutritious, particularly live foods. Always buy live foods from reputable sources. The likelihood of parasites is far lower.
Treat Fish With Medication
It’s best to use a broad-spectrum antibiotic to treat dropsy since the disease is so complicated. Broad-spectrum antibiotics can treat both gram-positive and gram-negative bacteria.
It’s very common to treat dropsy with oxytetracycline. It’s easy to find and is cheaper than many other medications.
Another way to treat dropsy is to combine Kanacyn and Maracyn or Maracyn-Two. Combining these two medications ensures the treatment targets both gram-positive and gram-negative bacteria.
Other effective medications include the following:
- Tetracycline
- Chloramphenicol
- Neomycin Sulfate
- Nalidixic
- Kanamycin
- Amoxicillin
- Doxycycline
ALWAYS follow the directions on the bottle of medication. All medications are different; we cannot give catch-all directions for medicating fish.
For best results, soak the fish’s food in medication if the fish is still eating. The fish’s body absorbs the medication more quickly when taken orally.
Medicate the water according to the medication directions if the fish isn’t eating. The fish’s body absorbs the medication through the water.
Most medications reduce the amount of oxygen in the water. Always use an airstone in the hospital tank, and perform a 25% water change daily.
How To Prevent Dropsy
Dropsy is notoriously difficult to cure. It’s best to prevent fish from developing dropsy in the first place.
To prevent fish from getting dropsy, keep their tank clean. Avoid stressors (like aggressive tank mates) and feed various nutritious foods.
Keep The Tank Clean
Aquarists should perform weekly to bi-weekly water changes. Remove about 15-30% of the water and replace it with fresh water.
During these water changes, scrub the sides of the tank and the decorations to remove algae. Clean the filter regularly and use a gravel vacuum to clean the substrate.
To keep the tank clean, avoid overcrowding. Always ensure there is more than enough space for every organism.
Check The Water Parameters
Check each species’ needs before buying them. Knowing their needs ensures you can create the ideal environment.
Know what temperature, pH, and water hardness the fish needs. Test the water regularly to ensure it’s staying within a healthy range.
Don’t Overfeed
Avoid overfeeding, which can dirty up the tank; only feed the fish as much as they can eat in two minutes.
Remove any extra food that remains after that timeframe.
Provide The Right Nutrients
Ensure fish get the proper nutrients by giving them variety and checking ingredients.
Only use flake foods up to a month after opening them, even if the container is still full.
Ensure live foods come from a reputable source. Doing so prevents the likelihood of parasites.
Is Dropsy Contagious?
Dropsy is not technically contagious, though other fish in the tank are likely to develop it.
Dropsy is usually caused by bacteria in the water. The bacteria has infected an immune-compromised fish.
Usually, if one fish is immune-compromised, the rest are, too, due to some kind of stressor.
Dropsy is sometimes caused by overfeeding or poor nutrition.
The other fish in the tank are still susceptible to getting the condition. Like the sick fish, they are likely eating too much or not getting enough nutrients.
How To Humanely Euthanize A Fish That Isn’t Getting Better
Dropsy is likely excruciating for fish. It’s kinder to relieve their suffering if they aren’t responding to treatment.
There are many recommendations for euthanizing fish online; they are not all humane.
Clove Oil
The best way to humanely euthanize a fish is with clove oil.
Begin by mixing a few drops of clove oil into the water to sedate the fish. Once the fish is asleep, add more clove oil to kill the fish.
About 0. 4 mL of clove oil per 1 L (0.25 g) of aquarium water is enough to kill most smaller fish.
Do not add all the clove oil at once. Add it slowly over 5 minutes to gently transition the fish into sleep and then into death.
The fish should stay in the mixture for at least 10 minutes to ensure they are dead. Wait to remove them until there is no more gill movement.
Clove oil can be challenging to find, especially at the last minute. There aren’t many stores that sell it, and “pure” clove oil without additives is even more rare.
Prepare for euthanasia when buying a fish. It’s not something we ever wish to do, though it’s better to be prepared when it’s necessary.
Being able to euthanize a fish immediately is kinder than letting them suffer.
Spiking — For EXPERTS ONLY
Another method is to “spike” the fish through the brain with a sharp tool.
Spiking is highly effective when done right. It is painful if the aquarist misses the brain.
We only recommend using this method if the hobbyist feels completely comfortable and knows what they’re doing. Any nervousness is likely to result in shaky. The aquarist may miss the brain and cause more pain.
Always know exactly where to penetrate before spiking, and act quickly.
Don’t Euthanize Using These Methods
NEVER euthanize fish with the following methods:
- Flushing down the toilet: does not cause immediate death & is bad for the ecosystem.
- Ice baths: painful & slow.
- Freezing: painful & slow.
- Boiling: painful & slow.
- Decapitation: painful.
- Suffocation: painful & slow (especially for betta fish, which can survive a couple of hours out of water).
