Between preference testing and inspection sessions, guppies were isolated in
breeders placed in 76 l aquariums to minimize preferences based on interactions.
The breeders were small, clear holding tanks which afforded physical, but not
visual, separation between individuals; visual contact was maintained to reduce
stress on the fish. After testing, inspectors and observers were housed in separate
76 l aquariums lined with gravel. Because so many male guppies were required
(270), approximately 10% of the previous inspectors were re-used, but only as
inspectors (never observers), never