Recently, i saw my dwarf gourami's fin on the bottom tip was getting brown and looked torn. His dorsal fin is just SLIGHTLY this way. I'm not sure what it is. Could it be fin rot? He's in a 10 gallon tank alone, Ammonia is 0 nitrite is 0 and nitrate is very low. He is acting normal and stuff too. I do a 10% water change once every other day(three times a week.) I don't know if this has anything to do with it, but I recently changed the filter cartridge, I did Saturday. Could this have done anything?