Dropsy Disease in Fish: Causes, Symptoms, and Treatment

Causes of dropsy disease in fish
The term 'dropsy' refers to the excessive accumulation of fluid in the cells or the tissues of the body, which in turn leads to the development of swelling. This Buzzle post provides information on what causes dropsy in fish, and how it can be treated.
Characterized by abdominal swelling and exophthalmos (bulging of the eyes), carp-dropsy complex is a condition that affects carps and goldfish. The causal pathogen for this kidney disorder is a parasite called Sphaerospora angulata. This condition can lead to complications such as carp swim-bladder disease or viral/bacterial infections.
Every aquarium owner should be aware of the fact that fish could become susceptible to various diseases if the water quality is poor. Also, they should learn about the specific needs of the species of fish they intend to keep in the aquarium. A very big mistake that new aquarium owners could make is to place a freshwater fish in a brackish or saltwater aquarium. To keep the fish healthy, one needs to learn about the important water parameters, such as the pH, temperature of water, carbonate hardness, hardness of water, ammonia levels, nitrate levels, nitrite levels, salinity, phosphate levels, etc. A sudden change in any of these water parameters can be the contributing factor for stress, which in turn can have an adverse effect on the health of the fish. For instance, dropsy, which is characterized by abdominal swelling, is a symptom that might appear in those fish that are exposed to poor quality of water for extended periods.

This symptom could appear when the water quality deteriorates on account of the tank not being cleaned on time. Bacteria could thrive in the presence of dirt or dead plants, which might increase the possibility of development of bacterial infections in the fish. Fish that are immunocompromised are more likely to develop dropsy.
Contributing Factors for Dropsy
Stress, which is one of the major reasons behind the development of dropsy, could occur under the following circumstances:
◆ Aggressive Tank Mates
Fish Tank
If some of the fish are more aggressive or territorial than the others, the latter might end up getting bullied. The aggressive fish might try to chase other fish so as to defend its territory and control access to food. In a small aquarium, there's hardly enough space for the other fish to go to. Under such circumstances, the weaker fish might get attacked. During such attacks, their fins might get torn, which in turn might put them at a greater risk of developing infections.
To prevent such a situation from arising, aquarium owners should ensure that the aquarium houses species that are compatible.
◆ Sudden Changes in the pH and Temperature of Water
pH value testing kit
While placing any type of fish in an aquarium, make sure that you learn about the ideal or the optimum temperature in which that particular fish will thrive. For instance, the optimum temperature range for goldfish is 68°F to 72°F. Placing it in temperature outside this range could cause damage.
Similarly, maintaining the right pH of water is also important. It helps to provide a safe and stable environment for the fish. It must be noted that pH will vary, depending on the species or the type of fish. Sudden changes in the pH can be very stressful for the fish; it can even cause them to die. It is extremely essential to analyze the water quality on a regular basis. If the fish tank is not cleaned regularly, accumulation of nitrate, nitrite, ammonia, and debris could take place.
◆ Improper Diet
Diet of Fish
Providing the fish with the right type of food, as well as the right amount of food is extremely important. You can feed them flakes or pellets. Make sure that pellets are not too large, and can easily be consumed by the fish. Pellets can sometimes sink, and if not consumed by the fish, these can get decomposed and adversely affect the quality of water. Keep the aforementioned aspects in mind while selecting food for the fish, and ensure that the food is nutritious.
While the characteristic symptom of dropsy is abdominal swelling, it could also be accompanied by other symptoms such as:
◆ Raised scales (Pinecone-like appearance)
◆ Pale gills
◆ Bulging of the eyes
◆ Lethargy
◆ Change in the eating habits
◆ Lack of energy
◆ Stringy, pale feces
◆ Fish floating near the surface of the tank
◆ Ulcers along the lateral margins of the body

In case of female fish, swelling could sometimes be due to the fish being egg-bound. Thus, it is essential to determine the underlying cause of swelling.
Treatment Options
Mortality rate is quite high, when it comes to fish affected by dropsy. However, when diagnosed in the early stages, the affected fish might respond well to the treatment.
Goldfish in Aquarium
◆ Though dropsy is not a contagious condition, it could be indicative of environmental issues. Therefore, it is advisable to place the affected fish in a separate tank. The benefit of using a hospital/quarantine tank is that it allows you to just treat the affected fish. If the medication is put in the main tank, it can reduce the number of beneficial bacteria.
Moreover, the medicines can also cause harm to the other healthy fish. Keeping the sick fish in a separate tank will also help it recuperate, especially if the infection was triggered due to attacks by other aggressive fish.
◆ Epsom salt or magnesium sulfate works as a laxative, thereby treating constipation. It also helps remove excess fluid from the body, thereby reducing the stress on the kidneys. So, put a teaspoon of Epsom salt for every 5 gallons of water in the hospital tank. Don't use Epsom salt in excess, as it could cause damage. If used in the right amount, it could prove beneficial for the treatment of dropsy in fish.
◆ If the underlying cause of dropsy is a bacterial infection, then you can put antibacterial fish food in the tank. You can also put antibiotics such as tetracycline hydrochloride in water. Affected fish can be treated with 40 to 100 mg of tetracycline hydrochloride per liter of water for five days. Keep the tank covered during this time.
In case of parasitic or protozoal infections, metronidazole (Flagyl) can be added to the water. Gradually raising the temperature of water to 80-85°F might help in preventing the growth of bacteria or pathogens.
Besides the aforementioned options, make sure that you check the quality of water on a regular basis. A water change of at least one-fourth of the tank volume once every month is recommended, besides the weekly change of up to one-fifth of the tank volume. Also, ensure that you don't contribute to any sudden changes in the water parameters while cleaning or decorating the aquarium. Dropsy can prove to be fatal in the absence of prompt treatment, which is why steps must be taken to treat it at the earliest.