I am a student at High Point Charter School in Sparta, WI. I am currently doing a project on yellow perch. The perch are held in a aquaculture tank. There were originally 100 perch in the tank,when we began this project in March. Within the last three weeks, I have lost 7 fish. When I remove them and study them, I notice that they have black marks on their tales. Their stomachs are completely flat. I would like to know what is causing these problems. Are the fish getting enough to eat? Is the water too cold? Is the temperature varying too much because the aquaculture system is in a greenhouse? Are the black tales caused by a fungus or something in the water?