Roland Bathes theory - Fish tank.

In fish tank there is a horse attached to chains that Mia makes several attempts to free. The horse signifies Mia in a way that it is usually an animal represented as free but is stuck on a chain & so cant do so, which is how Mia feels that she wants to be free but is stuck cooped up in a council estate where her mum would keep her upstairs when she'd have parties and punish her if she came down. It could also show innocence as it is white showing Mia's innocence as it dies after she sleeps with Connor.