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Identification and Treatment of Dropsy in Freshwater Aquarium Fish

Question about Dropsy:

I posted about a female Siamese fighting fish (Beta) that appeared to have dropsy a few weeks ago. I treated her twice with Maracyn. After the swelling didn't start to go down, but she is still as swollen as she was then, but has not got to the point were her scales have started to protrude? Do you know what else that it could be. She seems buoyant and the swollen cavity appears to be filled by either air, of a clear liquid, when she swims in front of the lights?


Have you tried Maracyn? Maracyn (Erythromycin) is usually not effective for most causes of Dropsy. And dropsy is generally a symptom of something else, sometimes digestive, often kidney related. Because of this, Dropsy can often be very difficult to treat, especially if caught in an advanced case in the fish. What the aquarist often observes is a "pinecone" swelling generally caused by fluid building inside the body cavity, for this reason, reducing this swelling is an important step in effecting a cure. This said, besides treatment for a possible underlying infection, you want to take steps to remove the swelling.

Here are the steps I would take:

  • Change water! (25% should be fine)
  • Perform a medicated bath with Methylene Blue. To prepare this bath I use 1 teaspoon 2.303% solution per 5 gallons (double dose) in a bath of aquarium water from the tank the fish you wish to treat came from, I usually use about a ? gallon of water, however you may use less. Measurement of the Methylene Blue does not need to be precise as this bath should be used for about 30 minutes (although do NOT overdose). Make sure you keep the water in a warm area, as in a cold room the water temperature can drop rapidly which would stress the fish. Do not pour this water back into your display aquarium when finished. This can be performed twice per day.
  • Add one tablespoon of regular salt (sodium chloride) per 5 gallons of tank water and ? to ? teaspoon of Epsom salts per 5 gallons of tank water. Add a Wonder Shell (trace element block) or similar product to add needed calcium. What these minerals will do is add electrolytes and change (and improve) the osmotic balance of the fish vs. the surrounding water to hopefully pull fluids thru the body thus reducing swelling.
  • Treat tank water with Kanamycin (Kanaplex), or possibly with Neomycin or Nalidixic Acid.

Here is more info about aquarium medications: Aquarium Medications; treatments, how they work, and which ones to use and not to use.


The aeromonas bacteria (that is often present in healthy aquariums) can cause infections that will manifest this way in poor water conditions. So maintaining a healthy aquarium with regular water changes, good filtration (if possible, this is why I see more cases of Dropsy in Beta kept in a bowl), good feeding practices (not over feeding and using quality foods), and maintaining proper water parameters (ammonia and nitrites 0, kH 80 ppm, nitrates under 40 ppm). All this goes a long way in prevention of Dropsy and other diseases.

A proper diet makes a large difference here. Do not feed your fish meat based proteins, I recommend aquatic based proteins such as white fish meal, shrimp or even the proteins found in spirulina algae.

As a basic diet I recommend Sanyu or Hikari Beta Gold (there are many other quality foods as well, although I do not recommend flake foods for betas as their staple diet) Poor quality proteins (or better; unusable amino acids for fish) can lead to digestive problems or Renal failure, which can lead to the symptoms of Dropsy. All proteins are made up of amino acids, some are usable (by fish), and some are not. Those that are not are disposed of by kidneys in the fish. This can lead to renal failure or infection. For more information about proper nutrition, see this article: "Quality Fish Food; What ingredients are needed for proper fish nutrition, growth and health". Also always soak all dry foods in water for 5 minutes prior to feeding as this will remove air that can lead to infections of the digestive tract. I would recommend this as a basic diet for your Beta: Sanyu Beta Gold.