Note:  This is a post from the www.koivet.com message board dated 01/17/2003.  The original poster wanted to know what to do with a fish with dropsy symptoms.  This was my answer:

 

Dropsy.. facts and fiction

This is as good a time as any to re-discuss dropsy. First, let's understand that dropsy is a clinical presentation of other problems and not a disease itself. Dropsy symptoms are caused by a gross increase in body fluid production. For the interested, this can be exudate or transudate fluids.. usually transudate. The excess fluid is produced because one or more organs are being disturbed and this disturbance is can be viral, bacterial, and/or parasitic. The increased fluid protection is an attempt to "cleanse" the affected organ with the fluid ending up in the body cavity.

The bad news about dropsy is that once you see the symptoms, chances are the damage is already done. But that does not mean that a fish cannot be cured. If the problem is bacterial, then maybe (BIG maybe) we can cure the problem with injectable and agressive antibiotic regimens. And then we wait to see if the affected organ can heal itself.

If the problem is viral, all bets are off and there is nothing we can do about it (reasonably)...

If the problem is parasitic, then we can try an aggressive salt regimen to get the internal parasites.. more later.

But how do we know the cause?? Well, it is possible to remove some of the fluid with a syringe and culture it for bacteria. But that can be a bit of a trick if you don't have a culturing capability. Viral we can't culture. And sometimes you can see a parasite problem under a scope... Removing the fluid is a rather easy process and in most cases will temporarily relieve some of the stress.

But let's say that you can't culture or remove the fluid. Here's a couple of tricks.. First, raise the salt level in a tank in 24 hour increments of .2% or so. This is two teaspoons of salt per gallon every 24 hours. Also, raise the tank temps to 82 deg F, optimal temps for the immune system to work. At .6% you should see some reduction in swelling and if the fish is handling the salt level OK, it should be perking up. Hold the salt level for 24 hours at .6% and if the fish is OK, set up a dip of .9% salt and place the fish in it for no more than 30 minutes and then replace it in the tank of .6%. These high levels of salt do two things... first, the salt increases in the body and helps with internal parasite reduction and second, the high salt will improve the osmotic process and may help the fish expel some of the excess fluid.

It also does not hurt to give an anti-bacterial injection, such as Baytril just in case the problem is bacterial.

Now for the problem at hand, I tend to think that it might have been the introduction of the pleco that induced the problem.. and this could be any of the three. But I like parasitic causes here )optimisim??).

Just because one fish gets dropsy, does not mean that anyone else will get it. It is rare that an epidemic of "dropsy" problems occurs and the problems are usually isolated to a single fish. However, it is always best to isolate the fish since treatment regimens are going to aggressive and best suited for smaller environments. The usual suspects that cause dropsy related problems are tpyically always in our ponds anyway.

And, it is also important to point out that dropsy type symptoms are reasonably common when water temperatures in the fall and spring (or unusually variable winters) are bouncing up and down. This is cold-water bloating and is caused by a mal-function of the osmotic process. If you see this and have experienced water temp fluctuations, I suggest that you remove the fish to a pond side .6% salt bath for 30 minutes and then send him back. An increased salt level will re-start the osmotic process and help relieve the problem. If it does not work the first time, you may have to remove the fish to a separate tank and longer exposure to increased salt levels.. A level of .3% works OK for longer periods of time.. also raising the tank temps to 65 or so will help too.