Different perception fields can result in varying behavioural strategies, collective behaviour, or ecological niches. However, limited research has been conducted on the effect of different perception fields within the same species, except for a few computer simulations that may not accurately reflect animals’ real reactions. This study aims to investigate the effect of different perception fields within the same species by attempting to expand goldfish’s perception of their blind zone. A blue circle was used as a visual signal to indicate the presence of another fish in the blind zone of the subject fish, and the response of the subject fish was recorded. Three experiments, namely the benchmark, main, and comparison experiments, were designed to determine whether this artificial visual signal could extend the goldfish’s perception fields. The results demonstrated that in the experiment with this artificial signal (main experiment), the situation that other fish appearing in the blind zone of the subject fish were significantly fewer compared to the experiment with random signals (comparison experiment) or no signals (benchmark experiment). These findings suggest that goldfish may be able to recognise the meaning of the artificial signal in the main experiment and use it to expand their perception and coordinate their actions accordingly.