Physical features of a seminatural environment on provoking various defence behaviour elements of the paradise fish were studied. It was found that most escape behaviour forms were under the control of visual stimuli. Transparent physical space induced escape and inhibited jumping. While the latter was induced by the presence of vertical untransparent surfaces. Dark places usually were avoided by the paradise fish. Placed into an unfamiliar environment in the presence of different escape routes the paradise fish seemed to make decisions after careful comparison of alternatives.