Sorry to get into this discussion late, but I have found that I get fish with dropsy in tanks that are being overfed. The water may look good, but there is excess food in the tank. If I do water changes including gravel cleaning on a routine basis, I do not get dropsy in any of the tanks.
I really do not like to use any medications in large tanks. If you are going to treat a fish with dropsy, do it in a small tank to which you have moved the fish with dropsy. You not only use much less medication, you can monitor the infected fish much better. Do not worry about the other fish in the display tank. Dropsy is not a disease that is easily transmitted to other fish. If they do not show signs of dropsy, they likely do not have it.
I have a theory about how dropsy gets to affect a particular fish. If there is excess food, not mulm, but food, on the bottom or in the gravel, there will be a high concentration of bacteria around it. When the lights are turned off at night, fish actually go to sleep or stupor with the lights off. Usually this means they settle to the bottom of the tank and do not move much during the night. If they happen to rest over the excess food, they are essentially bathing themselves in a high concentration of bacteria. Under the right, but certainly undefined circumstances, this bath leads to dropsy in the unfortunate fish which napped in the bacterial bath.
This theory not only explains how an individual fish gets dropsy, but also why most other fish do not, and perhaps, if the conditions are not corrected, why others in the same tank get dropsy at a later date.
Frank
I really do not like to use any medications in large tanks. If you are going to treat a fish with dropsy, do it in a small tank to which you have moved the fish with dropsy. You not only use much less medication, you can monitor the infected fish much better. Do not worry about the other fish in the display tank. Dropsy is not a disease that is easily transmitted to other fish. If they do not show signs of dropsy, they likely do not have it.
I have a theory about how dropsy gets to affect a particular fish. If there is excess food, not mulm, but food, on the bottom or in the gravel, there will be a high concentration of bacteria around it. When the lights are turned off at night, fish actually go to sleep or stupor with the lights off. Usually this means they settle to the bottom of the tank and do not move much during the night. If they happen to rest over the excess food, they are essentially bathing themselves in a high concentration of bacteria. Under the right, but certainly undefined circumstances, this bath leads to dropsy in the unfortunate fish which napped in the bacterial bath.
This theory not only explains how an individual fish gets dropsy, but also why most other fish do not, and perhaps, if the conditions are not corrected, why others in the same tank get dropsy at a later date.
Frank