For every April 1, there are two buttons on the tank. One is a yellow face with a moving finger and a message, "Don't click me!". Clicking on it will cause all objects to disappear and a message, "Happy April Fools!" will reappear. The second is a clown with a message, "Are you sure?". Clicking on it will cause the fish and other sea creatures moving in a reverse order without having an effect on crawlers, decorations, or animated props.