We analysed a sample of 4341 activity bouts from 12 male Nannostomus b. beckfordi interacting with ♀♀. Only 22 % of the gamopractic bouts ended in spawning. In 50 % of the bouts the pair separated without spawning or interference, partly as a result of male aggression. Interference frcm conspecifics was also a major cause of failure, terminating 28 % of the gamopractic bouts. Successful courtship bouts contain more gamopractic behaviour than do abortive bouts, even in the first 6 s, and also show greater stereotypy.