Oh my goodness, I just realised how amazing this poem is. When you open your eyes, stop being a child and become an adult, the fish don't disappear, they fall and die. It's becasue while we may lose our innocent, happier childhood view of the world as we grow up, it's still just as true as how we see the world now. The fish can't just disappear because they are real, to say otherwise would be to neglect our thoughts and emotions. Wow, all of a sudden, I love this poem, well done :)
I think you give this a little too much credit for what it is. But thank you for your comment.