On Wednesday I found one of my beautiful comets dead in my pond. I was sad but not too terribly concerned because he had always been a runt and never developed properly so I thought his disabilities had caught up with him as he looked perfect (for him) when I found him. The next day another died! I tested the water and the ammonia was elevated so I started doing water changes, a 50 percent water change to start and the next day did another 50 percent water change which brought the ammonia level down and I also added prime with the water change. Then this morning the last two were dead! I tested the water and ammonia was 0 nitrites was 0 and the nitrates didn't even register. What would cause that? Did I do the wrong thing with changing the water? It isn't cold here yet. They looked perfect, I am so sad.