A tropical fish that fluoresces bright red is set to become the first genetically modified pet to go on sale in the US. Alan Blake and colleagues at Yorktown Technologies LP say the GloFish will be available from January 2004. The little zebra fish were originally developed by researchers in Singapore to signal the presence of water pollutants by changing colour. "These fish were bred to help fight environmental pollution," Blake said. "They were bred to fluoresce in the presence of toxins." Blake and the scientists who developed the GM fish, which especially glows under ultraviolet light, say they pose no threat to the environment as they cannot survive in non-tropical waters. However, the news of the GM aquarium pet has sparked concern among conservationists. Buy them here.