The present study aimed to introduce barnacles as a behavioural bioindicator in Lake Timsah, Ismailia, Egypt. A special design is successfully applied for automatical monitoring of the barnacle cirral activities. Two barnacle species, Balanus eburneus and B. amphitrite, were collected for the present experiments. The observed typical cirral activities served mainly for feeding. Fast beats reached up to 100 beats per minute whereas normal beats were up to 50 beats per minute. B. eburneus exhibited circatidal rhythmicity under free-running conditions (continuous darkness and constant temperature). As an indicator of the pollution level, the cirral activity patterns were observed under different copper concentrations. Exposure to Cu2+ concentrations of 3.5, 3, 2.5, 2, 1.5, 1, 0.8, 0.6, 0.4, and 0.2 mg/L was achieved to determine 24, 48, 72, and 96 hr LC50 values. The LC50 values were 1.33, 0.635, 0.40 and 0.291 mg/L in B. eburneus whereas they reached 1.184, 0.493, 0.272 and 0.139 mg/L in B. amphitrite, respectively. The B. eburneus cirral activity pattern was directly and proportionally influenced by water copper concentrations at 24 and 96 hr LC50 conditions. It could be concluded that the cirral activity rhythmicity in barnacles, as an essential behavioural pattern, may be considered as a good tool for monitoring the pollution in Lake Timsah. The developed design may also be a useful tool for studying several environmental interactions of the barnacles.