you guys have got it all wrong, if you wanna kill a fish the first thing you have to do is get a cat.. doesn't really matter if it is your cat or the neighbours, bring him inside, put his little head up against the glass and show him your sick fish, at this stage your sick little friend has seen the cat and starts to panic, thinking to himself. i'm gonna be eaten and starts swimming really fast around the tank..
OK now that you have done this, it starts to get really trickey, you have to be able to grab the cat and in one fell swoop be able to lift the cat and insert him into the tank, replace all glass covers and the hood without him scratching you.
now comes the fun part, as you slowly watch the cat swimming around inside the tank looking like a rat, you will also notice that your fish is nowhere to be seen, at this stage he is hiding behind a rock shi**ing himself thinking that he was not that sick really and now wants to live.
after approx 30 seconds remove cat, feed your fish and i guarantee that your little mate will make a full recovery..
OH and removing the cat is optional!!!!!