I find this works well too. It is my supersecret 12 step way to catch a fish..
1. see unsespecting fish out and about.. think to yourself this is the perfect time...
2. slowly get up and try to get your net without the fish seeing you as they have tiny little fish brains they can't think hey mabye the guy who feeds me is trying to make me feel better but somehow they know what the net is
3. Try to jam net in tank at fish very fast..however as soon as the net hits the water it slows down on you and fish freaks out and heads to rocks.
4. fish gives little fishy smirk while poking head out of rock to see the frustrated look on your face. They love this part..
5. Curse in frustration and tell fish "fine if you wanna be this way then stay in there and be sick"
6. listen to fish laugh as he knows you are fibbing.
7. Try to talk nicely to the fish to see if you can coax it out say things like "come on little buddy I will make you feel better" and watch as he swims out just enough to make you think it will work...Only to go flying full speed back to the rocks..
8. Repeat step 5.
9. leave net in tank so you dont' have to risk jamming it in and giving an edge to the fish.. till you get tired of standing there after 15 minutesand decide to go get a chair or something..You'll get this fish yet..
10. Upon returning with said chair notice your fish magically in the net and he is asleep .. or so he would have you believe. He looks like he just swam in there on his own.. There is great rejoicing.. all you have to do is grab the end of the net..Unfortunatly as soon as your fingers get within 2 inches of the handle the fish suddenly swims full speed back to the rock....
11. Repeat step 5.
12. Decide heading to Aquariumadvice would be a much more level headed thing to do than going to your local army navy store and getting some cynaide.. You'll get that fish yet darnit