This title is part of Bug Club, the first whole-school reading programme that joins books with an online reading world to teach today's children to read. In this Blue-B level Mermaids book: Bella is worried about her pet fish, Twink. Twink is sad and doesn't want to play. Jo, Anna and Bella take Twink to see the octopus vet. The vet examines Twink and then holds her upside down. Bella is worried, but Twink coughs up a shell she has swallowed and then feels fine.