Dropsy is a disease that can show in even in the healthiest of fish with perfect water parameters, and is can be the end life of a fish that is near the average lifespan. Dropsy refers to a condition which creates abdominal swelling that can cause the affect area's scales to stand on their ends, which will give the fish a pinecone like appearance when viewing at various angles. Sadly there isn't much known about what fully causes the abdominal area to start swelling or what truly causes this to happen. Many researchers claim that it is due to the population of fish that are inbreeding due to high demand across all stores world wide, which would result in the fish's immune system and gene pool to be weaker than it ever would be naturally. Others claim this to only be a theory and put other things above the cause leading to a even bigger debate on this disease.
Since the first symptoms of this disease will be the fish being bloated, many confuse the bloat for having been feed too much, being constipated (and trying to use a method that will make the fish release their waste), and other times it may appear as if the fish is full of eggs or pregnant carrying fry. As this disease leads to its only known true symptom of the pinecone scales, one can fully conclude that the fish is infected with dropsy. However in most cases before the scales start to pinecone or even before the fish starts to get bloated, other symptoms do appear that will be traits of other diseases or infections, and if they are not cured will lead to the onset of dropsy. If no other symptoms are shown, then the finally conclusion is that the fish has reached its end of life naturally.
Since dropsy is normally the result of other diseases infecting the fish, if no medicine is given when the symptoms are shown then this disease can be contagious and infect all possible inhabitants that share the same water (including if any setups use the same equipment).
Sadly due to fact that this disease is not just one specific disease, but a grouping of various diseases or infections that have taken over the fish, it can be hard to know the life cycle which it will show. From various research studies done, there are some traits that all fish who have dropsy will show regardless of age, type of infections, of if they have any other diseases as well. The first stage is where the fish will start to look bloated, more and more as the days go by without really eating any food that is placed within the water. The final stage is when the fish's abdominal swelling will either get extremely large, or the swelling will go away and the fish will appear to have a bent spine or deformed body where both leads to the fish having a pinecone look appearance. If the fish is not euthanized once the pinecone appearance starts to form, the fish will start to loose scales, fins will start to fall off, the fish will spend most of its time at the bottom laying on the substrate before it leads to death.
Treatment and Medication
Unfortunately there is no known cure to this disease although many have stated that using a bacterial and fungus medication does slow down and can prevent death if given at the very early stages. The early stages include where the fish may be showing very little swelling, stop eating for days, have symptoms of other diseases, and even will be alone and not near or with any other inhabitants. There is no known documented proof such medicines do truly work once the first stage is reached.
Due to the way that this disease can spread and effects the inhabitants, the best prevention methods are to always make sure that you quarantine anything that you place inside of your water (this includes any plants, inhabitants, decorations, and more). Thus, when you do let them adjust to your water and you truly see how they are acting, eating and if they have any symptoms or signs, we will either start to get a better understanding if they are infected, or learn about what possible other diseases they might have.