Were the fish being sold gm medaka fish? If so i beleive they were injected with jellyfish genes so they glow. I think originally they injected the fish because a japanese scientist was trying to study how organ cells gather and devolop, so they made certain organs glow but after they team up with a company in singapore they started making these glowing fish to sell them to the general public. I think they're illegal because since these fish were sold for aquaria and not for human consumption if they are released into the wild and get eaten by another fish that is then eaten by a human or another animal, we don't know what harm could happen to the things that consume these glowing fish indirecly or directly.