the tank is 55 gallons, his tank mates never pick on him, he has a place to hide and everything, and of course the ammonia nitrite and nitrate are good as always, (0 nitrite, nitrate below 20), and all of a sudden today he hides in a cave where he never hides, and i see white spots on him, what does this mean?, and how did he get it??, none of my other fish have got it, and i even have more delicate fish than him, and none of them show these signs, he is 8" long, and is a BROWN AFRICAN KNIFE FISH, not the black one, is one of the knifes that grow to 8 or 10" only. also i have had LOTS of cases where my fishes in my other tanks got ick out of nowhere and for no reason, and then after a few days the ick was gone by itself. right now i just fed him some thawed bloodworms.