heres another good one for knives/loaches/catfish/etc as long as theyre not HUGE HUGE. take a 2liter bottle and cut the top off right where the neck meets the straight sides. then invert the neck and reattach it to the bottle with tape or staples. basically what you have done is made it so that the neck of the bottle no longer points out, but into the bottle. then drop some shrimp pellets, krill, etc inside the bottle and throw it in the tank overnight. next morning youve got a fish who cant figure out how to get out. i was going to try it for my clown loach but that damn thing is so friendly, i just pop the lid of the tank and dip my hand in and hell swim right into it thinking hes gonna get fed.