Sentosa Oceanarium, Singapore.
Pretty sure this is Lepomis gibbosus, but I'm not familiar enough with the other Lepomis species to confidently rule them out.
I agree with those who say it's a Long-eared Sunfish (Lepomis megalotis) rather than a Pumpkinseed Sunfish (Lepomis gibbosus). Both species are similar, but the Pumpkinseed Sunfish is a small species with a relatively short operculum with a small orange spot on the distal edge. The Long-eared Sunfish has the elongated operculum like this fish has, and the operculum usually has a yellow to orange margin rather than a distinct spot. Long-eared Sunfish are very widely distributed in the eastern U.S. and there are a lot of regional subspecies, which makes their identification even harder. Also, Long-eared Sunfish often have a red background color on the head, which is usually lacking in the Pumpkinseed Sunfish.
Thank you for taking such a good photo because it helped with the identification! I believe that Pumpkinseed Sunfish are established and an invasive species across a lot of western Europe, so it makes sense that they would be featured in aquariums over there.
