This is huge in Japan and recently landed in Singapore as well, and I tried it out a while ago at Underwater World. They have two kinds of fish, the normal (well, for flesh-eating fish, anyway) Turkish kind and the more "aggressive" (their words) Mozambiquean fish -- the Turks were nibbly and ticklish enough, but having a few hundred African fish with mouths the size of my pinky nip and poke at my legs felt so weird that my feet kept bouncing out of the water due to sheer reflex. It was also empirically determined that they like hairy, stinky guy feet more than silky smooth, nice-smelling lady feet. Let's see when they come up with a beauty treatment involving piranhas...