Alright, hasn't this thread gone on long enough?
There is no such thing as a "Fish Pet". There are no fish characters programmed ANYWHERE on the V2 OR the V3 for that matter. There isn't even a fish character on the Akai! The only Tamagotchis that have ever even remotely resembled fish are those on the Tamagotchi Ocean/Umi No/Oceangotchi, which was produced way back in the 90's.
There IS a dog one named Puchitchi on the V2, there's a cat one named Nyatchi on the V3, and there's even toilet-themed ones on the Uratama! But no such "fish pet" exists, and I truly feel sorry for anybody that believes in it. Whaletchi is not a fish either, he's moreover a lump of moss labeled as a whale.
No special foods will get you a fish pet, no starving costume characters will get you a fish pet, no debugging, no ROM testing, no mating teens with adults, NOTHING! There hasn't even been any photographic evidence of these Fish Pets!
This pointless, go-nowhere thread was made almost 2 years ago, and it's about time that somebody closes it. And unless any one of you can get proof of the so-called Fish Pet, it better be good enough evidence that you could show it to Bandai and hear them say, "Yup, you're right, there's a fish pet!"
*thread closed*