Unfortunately boy passed away sometime during the night

. The tank looks so empty without him. He used to be so naughty like getting through the divider and 'owning' both sides of the tank.
Since I was concerned that he might have been infected with something transmittable, I poked his stomach with a pin to see if anything came out. Oddly enough, it was just all air (or clear fluid I couldn't see) and deflated back to its usual size. I'm suspecting there was some underlying organ failure or damage that caused his death.
Hopefully I don't see anything like this again. I think I'll just hit it right away with anti-bacterial meds instead of messing around with salt and fasting.