Cherry barbs dying one by one

[cwt]

Strange doings in the cherry barb tank (20 tall, tank has been in service for a few months). Last week, found one male dead, stuck to the filter intake, with a large red bulge in its rear quarters. Wasn't sure of any persistent problem, so I did a water change and let it go. Today, I see a similar mark on the underside of the second male. The only other inhabitants are 3 females, and 3 mystery snails. Did the snails bring parasites with them, and how should I approach this? Will post a pic when I get a chance.

 

[Big Dog]

Snails can bring parasites with them. Post some pictures which should help us out a lot.

 

[cwt]

Looking at him today, the second male's problem looks more like a bite, which is already healing. He's been very aggressive since the other one died, and one of the females probably gave him notice. Hopefully just a false alarm. Still don't know what the first male died of, but the females are all healthy, so it's just something to watch for now, I guess.