It seems avant-garde for those times, still a bit immature for our times. It didn't keep its original strength. But maybe is my general aversion to films from the late 60's/70's. Something about the photography/sound usually makes me feel bored and not focused even if the story is great.
Although 'American Honey' has to be placed in a different level, 'Fish Tank' was very pleasant to watch. I admit that the word 'pleasant' seems strange in this context, but the story has enough hopeful moments and beautiful holes that made it somehow light in my eyes. Besides that, the rhythm is just perfect.