Sorry to hear. Maybe it had a parasite or some adverse reaction to the food?Fluffy was doing great. Eating, exploring, good color etc. then he just died. His water was fine, I just don’t know what happened. Bad week for puffers. I had to put my miuris and suvattii together in a 55, and I used a light diffuser grid to separate them. The miuris got over it somehow and got half his face ripped off. Sigh.