I do have a couple of Tilapia with blotches on their heads. But then I have one albino too. From the looks of the guys tank I bought them from I'd say they were raised in pretty filthy conditions. For the past week I've been feeding my fish heavily and the water seems to be staying clean. The very first time I tested our tap water the ammonia was almost 1/2 ppm. My neighbor happened to be talking to the water company and they told him that they added extra chlorine to the water for some reason or another but I guess it was just a freak occurrence. I've never been able to measure any ammonia since that day in the tap water.
