Okay, after the neon tetra disaster a couple weeks ago, I got a dwarf gourmie this past weekend. Everything was going well until yesterday when I noticed he has a white patch behind one of his gills, and he is starting to hide. It doesn't look like a fungus though--not fuzzy. Upon really close inspection it looks like his gills are white and puffed up, and it is red around it. I guess it looks like a sore. It has not grown at all in size since yesterday. Ammonia and nitrite are holding steady at 0. I don't have a hospital tank yet, and I am hesitant to medicate the whole tank when all the other fish appear healthy. Any suggestions?