Fluctuation of the seagrass ecosystem may be informative to the impacts of environmental changes. This study focuses on a small, inconspicuous triplefin blenny, Enneapterygius minutus, found in a specific tide pool of seagrass meadow on Gui Wan Bi, Green Island, Taiwan. Its high abundance and stable residence make this species a suitable candidate to monitor the condition of the seagrass ecosystem. Monthly collections were made during low tide from April 2007 to July 2008. The otolith microstructure was examined to study their age and growth circumstance. Developmental stages of the ovaries based on histological characteristics together with data of batch fecundity and GSI value were applied to estimate size at maturation and the spawning seasonality of the individual assemblages in the tide pool. A length-frequency analysis was made by using the monthly data. Enneapterygius minutus is a kind of short life species. It has a quite low batch fecundity and a year-long breeding ability with a seasonal high peak mainly from late winter to late spring. The recruitment of juvenile individuals began about a month after breeding had occurred. These data show that Enneapterygius minutus uses seagrass meadows as a hatching and nursing habitat. According to the close relationship between Enneapterygius minutus and seagrass meadow, it would be possible to monitor this ecosystem by using this species as an indicator when it is under environmental stress.