I have a 30 gallon tank with 4 silver dollars and 1 gauromme. The tank population has been stable for 18 months. Yesterday I noticed one of the silver dollars with 2 flesh-colored swellings on the right side. The larger one is about 3 mm at widest diameter. The skin is not broken, and the fish seems to swim well but is not eating as well as usual. I had the pet store test the water. They said the nitrates were 'borderline' and I need to change the water 20% for 3 days in a row. They suggested I isolate the silver dollar, so I have him in a one gallon tank now. He has not changed any in the last 24 hours. The others in the original tank still seem well. The person at the store suggested this is either some type of 'nodular disease' caused by parasites, for which there is no treatment. Does anyone have a suggestion as to what caused this or what to do next?

Does the swelling look hard of soft like filled with fluid.
What does it look like when the fish goes to the toilet.
Check the fish anus to see if its enlarged or red and inflamed.

This post has been edited by Wilder: Jul 2 2008, 07:04 PM

Thanks for the reply. The swelling does not appear hard or irregularly shaped. It does appear like it could be fluid-filled. The area where the anus should be does not look red or inflamed. I really cannot see exactly where it is. I have not seen the fish have a stool in the past day, but there may be a piece of stool floating around the water that appears normal. The bumpy areas are not reddened themselves, and the skin is not broken.

All you can do is try a bacterial med but you will need an airstone for aeration, as med
reduce 02 in the water.

Thanks again. Yesterday I got some type of general bacterial med and airstone. Nothing has changed now in about 3 days. Could the fish be constipated, or would that give a more symmetric swollen area?

I would give the med abit longer to work.
You could try some peas.
Cook frozen peas for a few minutes, let cool down, pop out of shell and mush between fingers then add to the tank.

Thanks again. I put the silver dollar back in the tank with the others. No other fish seems to be infected. Over the last 48 hours, the smaller of the two bumps seemed to disappear completely, and the area where the bump was is now replaced by a flat black spot. As for the larger swelling, over the last 24 hours, the skin over the swelling seemed to peel away leaving some whitish material exposed. Just this morning, as I was watching the fish, the whitish material fell off the fish, and now there is a large black spot where the large swelling used to be. From what I can tell, he is still acting normal, schooling with the other silver dollars, and eating. Does this sound like an infectious disease, or something else? THanks

I would take him out of the main tank.
Does the patch look like it being eaten away.
Any signs of flicking and rubbing.
If not I would carry on with the bacterial med, if its a flesh eating bacteria you will
need antibiotics.
Any redness to the patch.
Red sores and patches can soon ulcerate the skin into holes.

When you issolated the sick fish do some water changes on your main tank.

Thanks again for all your help with this. This is the first time I have had an obvious sick fish.

If I take him out of the main tank, would he be ok in a one gallon tank with aerator? That is the only other tank I have. How do you keep a small tank like that clean?

The dark patch, where the smaller swelling was, seems to be partially fading back to skin color. Where the larger bump was, the skin is kind of wrinkled, like a bunch of loose skin that used to be stretched out. The center of that area appears to be a hole with a small amount of whitish debree sticking out. That whitish stuff is the same color as the flakey stuff that fell off yesterday. This has not changed in appearance in 36 hours, and it does not appear that an active process is eating it away, as the area in not enlarging. There is no apparent redness. I have watched closely, and there appears to be no signs of flicking or rubbing. Fortunately, there does not appear to be any new lesions either. The fish does not seem to be acting differently than the others and is eating.

He sounds in a bad way.
Take a look here.
http://www.fishyfarmacy.com/articles/aeromonas.html