Photo: Alex_Vinci/Depositphotos(Not a photo of the actual Mambo the sun fish.)

At first, the staff couldnt determine the cause of his strange behavior, despite experimenting with different approaches.

Initially skeptical, the aquarium staff doubted the fishs loneliness.

Japanese Aquarium Lonely Sunfish

Photo: Alex_Vinci/Depositphotos(Not a photo of the actual Mambo the sun fish.)

Real staff members also took the time to wave at Mambo to try and raise his spirits.

Much to their surprise, Mambo appeared to be in good health the very next day.

Check out the amusing photo below and followKaikyokan Aquarium on Instagramfor more updates on its aquatic friends.