When Emma drinks from the vase, it's clear. When Lewis takes it from her, it's green.
Emma gets Cleo a piece of coral for her new fish tank, but the new tank is freshwater. Coral needs to be in saltwater to survive.
When Cleo is first telling Emma and Rikki about her new goldfish Hector, she says she only feeds him a pinch of fish food "so he doesn't put on weight". But later when she feeds him after he starts acting weird, she dumps in a fistful of flakes.