Hey ok I have a cold water tank with 3 fantails the tank is 40 gal. One of y gold fish has a spot just like a human spot and its very visible its about the sice of a qaurter of a finger nail (only thing I could think of). The fish with the spot is fine and swimming hapily BUT.. the other gold fish is swimming very slowly and near the bottom. I have medicated the tank with 2 things swim bladder control and white spot treatent altho its not white and very big. what do I do ? Any Ideas ?