I woke up this morning and my beautiful Green Terror was dead. I have had him for almost 2 years and he has always been a healthy strong fish. He has survived 2 moves (not recently) and always looked great. I dont understand why he would just die one day. The water stats are perfect (ph, ammonia, nitri, nitra) and i do water changes every other saturday. An albino convict is in the tank with him as they were brought home together and have lived together for the entire 2 years.
He died sometime between 1130pm and 630am. At 1130 he was fine and had just eaten some Hikari Cichlid Gold. He didnt have any open sores, gashes, etc this morning. When i pulled him out his stomach was a tad bit puffy but he was not extremely bloated, his eyes were white and his skin pale (figured this was caused by sitting in the water) and his mouth was closed. I have kept fish for a while not and when i have lost fish in the past it was pretty obvious of what had caused it.
Is there anything else i can test the water for? What about the Convict?

He died sometime between 1130pm and 630am. At 1130 he was fine and had just eaten some Hikari Cichlid Gold. He didnt have any open sores, gashes, etc this morning. When i pulled him out his stomach was a tad bit puffy but he was not extremely bloated, his eyes were white and his skin pale (figured this was caused by sitting in the water) and his mouth was closed. I have kept fish for a while not and when i have lost fish in the past it was pretty obvious of what had caused it.
Is there anything else i can test the water for? What about the Convict?