disease or not?

[wal999]

I have a silver dollar with a small lump or bump on his side. I 've tried to look up diseases that fit. All I come up with is Argulus(fish lice). I was going to treat him in a separate tank, but upon reading about these critters, it sounds like I need to treat the entire community. First, anyone know if this is truly Argulus or some type of a parisite? Second what treatment is best, without killing my bio filter?

 

[tetra girl]

does he emit any strage behaviour? for example flashing or rubbing? Is he still eating properly? is the bump a different colour or is it his skin? what are your water paramters?

 

[wal999]

symtoms

He doesn't flash and is eating OK not quite as much as the other dollars. The "lump" appears to be the same color as skin. Water parameter are right on. PH-7.0, Ammonia-0, nitrites-0, GH-5. No other fish in the tank show signs of stress.