A major life-history challenge for fairy shrimps (Anostraca) is the unpredictable environment of the ephemeral pool. The duration and predictability of pool inundations affects their life history strategy. The growth and reproduction schedule of a thamnocephalid fairy shrimp, Branchinella (Branchinellites) kugenumaensis, in an unpredictable ephemeral pool in northern Taiwan was monitored from 2004 to 2008. A total of 15 inundation episodes, resulting from typhoons or, occasionally, frontal systems, was recorded over the five-year period. Thirteen episodes lasted no more than 2-3 weeks. Two exceptionally long inundation periods were caused by additional rain events before the pool dried out. We recorded the growth patterns, egg spawning time, and clutch size of each fairy shrimp cohort during each inundation episode. No significant differences were observed in either growth or reproductive pattern from hatching to first spawning between short and long inundation episodes. The fairy shrimps stopped increasing in size during the first clutch production. Upon subsequent rainfall before the pool dried, the shrimp stopped reproducing and resumed growth, demonstrating a discontinuously indeterminate growth pattern, before resuming egg production. Body length was positively correlated with clutch size, and this can be expressed as clutch size  =  0.0059 body length^3.165. The potential reproductive fitness of this indeterminate growth strategy demonstrates optimal resource allocation between growth and reproduction.