eh i think using live goldfish abit exp leh and they cant survive in salt water very long .. if they die inside without the shark knowing then u will have trouble getting that little guy out.
y not juz go to the market buy some small nasi lemak fish ... use a string and tie it to the mounth.. use a knife make a cut it in and it the blood flow... then wiggle that fishy around... SHARK SMELLS BLOOD sure wack like there is no tomorrow ... haha
juz using my imagination dunno whether it will work