Aquarium by DS Cheats :
Secret - Mermaid and Diver
Have a friend with fantasy aquarium by DS to breeed lots of his fish. when he gets enough, he can unlock mermaid and diver but he can only get one per game. Trade something for them and you have mermaid and diver. You can also do this to get fantasy aquarium fish to an aquarium file and vice versa. Have fun!