My 2 year old betta fish has recently become very sick. I have no idea whats wrong with him, but he just keeps laying on the bottom of his tank and it seems that he can't swim. Whenever I drop flakes in the tank, he trys his best to swim to the top but just sinks back down, and I havn't seen him go to the surface for air in days. At this rate, I think he will probably starve if his illness doesn't get to him first...I was wondering, what would be the most humane way to kill him so he doesn't have to suffer anymore?