I brought 6 powder blue gouramis home from the store yesterday, and after doing some research I think they are all male. I noticed one possibly two I think have fin rot. I bought them at pet smart, so I have a 15 day return policy. From my research it seems males would fight eachother when they get older, although peaceful toward eachother now. Then there is the problem with the fin rot. One has a little notch out of the back fin, and the other looks a little jagged. I suppose it could be from fin nipping but I have seen zero of that going on. I had to wake up my son and husband this morning so we can be at the store as close to 9am as possible to return all but one. I am wishing I had a fish store that was more informative instead of selling me 6 males, one or two being sick. I'm going to look around for another pet store, but two others I know are probably less reliable. The other store told me I could put 16 electric yellow cichlids in my 30g tank. I decided then that it would be a bad idea for me to buy fish there. I have zero cichlids btw. I decided against them. Out of the 6 fish, there might be one female because the doral fins are shorter and rounded but it is very powder blue in coloring, and from what I've read females are pale. My 11 year old son is very understanding and he has studied fish diseases, and understands that the males may fight when they get older. He is fine with taking them back to the store, I'm so glad he's not as disappointed as me. My dog was comforting me even. Oh well, brightside is my son gets to pick out other types of fish. Firstly though, I am going to treat the tank with fish medicine. What do you recommend for treatment? I plan on keeping the best looking one.

Formalin-3 and maracyn are supposedly good all around meds. If your stores are like mine, I can only find these on the internet. Although, my Petco was out of maracyn but they normally carry it. Don't have any experience with either...have just read of good results with them.

Or you could try melafix as well, it is more benign to the tank if you dont have a hospital tank to move the fish for treatment.