I lost my 8 inch red sev female in January----I loved that fish! Got Rosy when she was about the size of a silver dollar--had her almost two years. She would follow me around the room from her tank. When I would sit in my lazy boy chair near her tank--she would tap the aquarium lid to get my attention. Then there was my 10+ tire track eel--Cooper---Loved him to pieces. Silly thing would stick his head out of the water when I'd talk to him, eat from my hand. He would kind of slither around my arm when I'd mess with any thing in the tank or do water changes. The husband called Coop the tank supervisor.
Rosy was fine one night--and when I woke up the next morning was floating! No marks--no nothing! She went to the fish graveyard out back--my husband gets burial duty.
Cooper was my fault. I thought all the Kuli Loaches were gone from the tank before I got Cooper---wrong! One night Coop starts thrashing and hitting the sides of the tank. I freak out--the husband nets him---Coop was bleeding from the mouth, and died shortly. Husband looked down his throat, and there was the damned loach. I was crushed---haven't gotten another eel since.
I've had others die---cory and betta, but Coop and Rosy just broke my heart. I asked at my LFS what could have killed Rose----water was perfect, but they said sometimes they just die.