Completely agree with this, a tank I would presume. But they're pretty amazing nevertheless.
BTW Andy Rouse said in a talk I heard him give that he used a tank for some of his kingfisher shots too - after days on end of blazing away with the motor drive at point of impact and getting knowwhere he resorted to it. Not a problem in my opinion if it doesn't hurt the bird, the fish are humanely kept prior to their "sacrifice" and it means even one more person is turned towards wildlife conservation as a result of some inspiring photos
