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Deadly Dropsy Fish Disease

How to care for fish that have come down with dropsy.

By Stephen M. Meyer

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Q. My favorite goldfish, Molly, is about a year old. She is a good-size red-and-white oranda. Molly has developed dropsy. I've spoken to several people, including the owner of the local aquarium store where I got her, and all have said to euthanize her. I don't want to do that. Is there a cure? I found several products in the aquarium store that say they treat dropsy.

A. Advanced dropsy is a severe internal bacterial infection resulting in a generalized septicemia. That is, the bacterial infection and bacterial toxins permeate the bloodstream and move throughout the fish's body.

In goldfish the infection almost always begins in the intestinal tract, caused by the bacterium Aeromonas hydrophila, (other species, such as Pseudomonas, can cause similar problems). Bacterial toxins break down intestinal tissue, and fluids begin to fill the visceral cavity. Progressively, the bacteria destroy internal organs.

Chances are that by the time you notice a real problem — severe bloating and standing scales — the damage has been done. Nothing will help at this point. The only sensible course of action is to euthanize the fish.

But, before you put the fish to sleep, make sure the problem really is dropsy and not some treatable problem. Often, the external signs we associate with dropsy — bloating, scales standing out from the body, balance problems — also appear under other circumstances. These false instances of dropsy account for the "miracle" cures reported in the hobbyist literature. They are really not curing an Aeromonas sp. bacterial infection. (Yes, if caught very early medicated foods can cure this bacterial problem. But, in almost all instances, hobbyists do not notice the problem soon enough.)

Some goldfish are just fat and odd-shaped. They look weird and swim weird. However, in fat goldfish, the scales do not stand out from the body as they do in cases where abnormally high visceral pressures push out the scales.

Some female goldfish can exhibit dropsy-like symptoms at breeding time. I have a female fantail who does this every year at breeding season. As her eggs ripen, her abdomen swells, scales stand out and she has great difficulty swimming. Once the eggs are expunged, however, she returns to normal in a few days.

I also have a beautiful female koi who exhibits the same signs at breeding time. The first time I saw this I resigned myself to euthanizing her sometime in the subsequent weeks. But, it was never necessary. That was seven years ago.

So, let's be sure the problem really is dropsy. In advanced cases the abdomen has no firmness. When you touch it with your finger it feels like a plastic bag full of water. Scales may fall away and blood will seep from the touch point or, equally likely, from the anal vent.

An internal tumor (or large tape worms) may cause similar bloating and standing out of scales. And, for the most part, there is nothing you can do about tumors either. Some tumors are slow growing, others expand rapidly. Euthanizing the fish is the most humane thing to do.

The only sure way to tell if the problem is intestinal worms is to actually see worm segments dangling from the anal vent. A veterinarian can provide treatment for internal worms.

All of this begs the question, how do you euthanize the fish? There are many ways to do this, but the one I recommend is to put the fish in a container of water and stick the container in the freezer. I suggest that you do this when no other family members are around.

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