In this film, Andrea Arnold has demonstrated her mastery and fluency in the social-realist idiom, and simply makes it fizz with life. Having now watched Fish Tank a second time, I am more exhilarated than ever by Arnold's idealism, and in a movie marketplace where so much is vapidly cynical, this is a mistral of fresh air. Arnold finds a way into the fashionable notion of a "Broken Britain", but in place of the pundits' dismay and contempt, she offers tenderness and hope. If Ken Loach were ever somehow called on constitutionally to nominate a successor, it would surely have to be Arnold. She's got the grit; she has Loach's humanism and optimism and she has a happy knack of getting great performances out of her cast, particularly from Michael Fassbender, who proves that he's not just sex on a stick – he's complexity and vulnerability on a stick as well. Added to this, Arnold and her cinematographer, Robbie Ryan, conjure some glorious, almost Turner-ish images of the Essex countryside, with its racing summer skies.

At the centre of the story is newcomer Katie Jarvis, playing Mia, a tricky, lairy 15-year-old in trouble with the social services for breaking a girl's nose after a contretemps in one of the windswept municipal canyons lying between tower blocks. She has inherited from her mum, played by Kierston Wareing, a stroppy insecurity and a nascent fondness for the booze. The family dog is actually called Tennent's. Mia has a feisty younger sister, Tyler – a scene-stealer of a performance from Rebecca Griffiths – who is always winding Mia up with shrill threats to "tell on her". There is no dad in the picture. Mia has just one interest in life: urban dance, and she isn't too bad, but the moves she practises are moody, introverted and subdued, rather like the dancer herself. Their torpid lives are disrupted when Mia's mother miraculously gets a new boyfriend, Connor: and Fassbender gives his best performance yet. Connor is funny, sexy, confident and utterly relaxed where everyone else appears clenched with resentment.

Noticeably articulate, Connor appears to come from a marginally more middle-class world and he is also, tellingly, a breadwinner. Mia rifles through his wallet while he's upstairs with her mum and instead of immediately nicking the cash, she gazes fascinated at his payslips: a man who actually works for a living. How many of those has she ever met? Without consciously realising it, Mia is hoping that Connor could be a father-figure, and both sisters are secretly thrilled when he takes them all out for a drive in the country, and shows them how he can catch a fish with his bare hands. big fish tanks for sale ebayWhile her mother and sister cringe on the riverbank, Mia wades out into the cold, slimy water to help him and Tyler squeaks: "Is it minging?"fish tank ebay singapore No, it is not minging. aquarium in uk with sharks

It is sensual and exciting, an exotic experience such as Mia has never known. And it marks the decisive point at which Connor and Mia's relationship drifts past being that of a quasi-father and daughter. Connor even takes an interest in her dancing, and casually lends her his expensive camcorder to tape an audition for a local competition, trusting that he will get it back. "You dance like a black," he tells her, with studied, flirtatious insolence. "I mean it as a compliment." Mia has an enormous, poignant capacity for love, but she has never received any, certainly not from a damaged mother, whose one moment of intimacy with her daughter comes when she ferociously tells Mia that she was thinking of having her aborted. So she has no idea how to express or manage love and it is her muddled, suspicious longing for the safety and comfort of a father's care that makes the situation so explosive. As for Connor, it is far from clear how much baggage he has: he moves in to Mia's mum's flat because he says his own mother has thrown him out and often has to take calls from his "mum", but what is really going on?

It becomes all too clear that if Mia has her own issues about family, then so does Connor – whose secrets are shabbier and more poisonous than either Mia or her mother could have realised. The situation heralds an unwatchably tense finale as Mia's adoration turns into anger and then a determination to survive, to outgrow her surroundings, and to forgive. Arnold shows us that what makes the relationship between Mia and Connor so transgressive is not their obvious sexual attraction but their quite genuine, if thwarted and delusional longing to be father and daughter. Jarvis has given a wonderfully honest and open performance to be compared with David Bradley in Kes, or Émilie Dequenne in the Dardenne brothers' Rosetta. Her relationship with Fassbender is what gives the film its beating heart.Andrea Arnold's piercing "Fish Tank" is the portrait of an angry, isolated 15-year-old girl who is hurtling toward a lifetime of misery. She is so hurt and lonely, we pity her. Her mother barely even sees her.

The film takes place in a bleak British public housing estate, and in the streets and fields around it. There is no suggestion of a place this girl can go to find help, care or encouragement.The girl is Mia, played by Katie Jarvis in a harrowing display of hostility. She's been thrown out of school, is taunted as a weirdo by boys her age, has no friends, converses with her mother and sister in screams and retreats to an empty room to play her music and dance alone. She drinks what little booze she can get her hands on. And where is her mother? Right there at home, all the time. Joanne (Kierston Wareing) looks so young, she might have had Mia at Mia's age. Joanne is shorter, busty, dyed blond, a chain-smoker, a party girl. The party is usually in her living room. One day, she brings home Connor (Michael Fassbender), a good-looking guy who seems nice enough. Mia screams at him, too, but it's a way of getting attention. Joanne seems happiest when Mia isn't at home. The girl wanders the streets and gets in a fight when she tries to free a horse chained in a barren lot near some shabby mobile homes.

She surfs in an Internet cafe, goes to an audition for sexy dancers and breaks into a house at random.One day differs from the routine. Connor takes Mia, her mom and her little sister Tyler (Rebecca Griffiths) on a drive to the country. This isn't an idyllic picnic; they simply park in a field and hike to a river, Joanne staying with the car. Connor takes Mia wading ("I can't swim") in the river. Walking barefoot, she gets a ride on his back and rests her chin on his shoulder, and what was in the air from the first is now manifest.Some reviews call Connor a pedophile. I think he's more of an immoral opportunist. "Fish Tank," in any event, isn't so much about sex as about the helpless spiral Mia is going through. The film has two fraught but ambiguous scenes -- one when she goes to Connor's home, another involving a young girl -- that we can make fairly obvious assumptions about. But the movie doesn't spell them out; Arnold sees everything through Mia's eyes and never steps outside to explain things from any other point of view.

She knows who the young girl is, and we are left to assume. Whatever she thinks after the visit to Connor's house, we are not specifically told. The film so firmly identifies with Mia that there might even be a possibility Joanne is better than the slutty monster we see. A slim possibility, to be sure.In a film so tightly focused, all depends on Katie Jarvis' performance. There is truth in it. She lives on an Essex housing estate like the one in the movie, and she was discovered by Arnold while in a shouting match with her boyfriend at the Tilbury train station, which is seen in the movie. Now 18, she gave birth to a daughter conceived when she was 16.We can fear, but we can't say, that she was heading for a life similar to the one Mia seems doomed to experience. Her casting in this film, however, led to Cannes, the Jury Prize, and contracts with British and American agents. She is a powerful acting presence, flawlessly convincing here. And Arnold, who won an Oscar for her shattering short film "Wasp" (2003), also about a neglectful alcoholic mother, deserves comparison with a British master director like Ken Loach.