HAHAHAHAHAH
While the bluegills have successfully detected at least 30 toxic chemicals, they cannot reliably detect germs. And they are no use against other sorts of attacks -- say, the bombing of a water main, or an attack by computer hackers on the systems that control the flow of water.
HAHAHAHHAHAHA. Oh noes! Just wait until the blue gills are able to detect crackers in the computer system. Probably will require the blue gills to have lasers on the top of their head.