Anemonefishes are immediately recognisable by their striking colour patterns, all of which adhere to a basic theme. This is an orange, red, yellow, or black body, with up to three white vertical bars. These colour patterns develop during metamorphosis and can change as the fish grow from juvenile to adult. Additionally, plasticity has been observed in the colour patterns of adult fish under certain conditions. Studies have shown false clown anemonefish Amphiprion ocellaris (orange body with 3 white bars) are able to distinguish between approaching fish based on the number of white bars they possess, which has been linked to their classic territorial behaviour. This raises questions related to the fishes’ cognitive abilities, specifically to do with pattern and individual recognition. Here we investigated the aggressive response of wild-type A. ocellaris when faced with intruding fish that had the same number of white bars but varied body colours or bar shapes (e.g., a melanistic morph or "snowflake" mutant). Through experiments with live fish, we found that regardless of body colour and bar shape, WT A. ocellaris were more aggressive towards individuals with three bars. This remained true for novel intruders and across repeat exposures. This confirms that number of bars is a key component of inter- and intra-specific interactions in anemonefish. Using these results as a baseline, we are developing a realistic computer model to replace live intruder fish in such experiments, which will increase experimental efficiency and allow more in-depth analysis of anemonefish recognition in future work.