While feeding my fish this morning before I left for work, I noticed the white patin is lifeless at the bottom of the tank. It was still alive yesterday evening but refused to surface to feed which I thought unusual. So there must be a disease or something that only affect this kind of fish. Patin has smooth skin unlike other fish in the tanks, the others are scaly type. I'll check the tank thoroughly today to see if there is any abnormality to the other fish. No more patin left. Farewell my friend.
UPDATE 21/11/12: I checked the tank yesterday and found nothing is wrong. However one of the Koi has two grey spots on its back, not sure if it is infection or just the natural colour of the scale. I will monitor that one closely.