I have a pink kissing fish and he eats all my other fish and he doesn't get fed as often because I'm not here all the time. I feel really bad, but the pet shop won't take him back. I can't keep him and I know this sounds really horrible, but I have to "put him down". It's better than him starving to death. So if I just unplug his filter, we he die peacefully and painlessly. If not, how can he die painlessly?