The smallest minnow
Is food for the largest shark
It's still important
That's my work, unfortunately. It follows all the rules, even the most difficult one: the first line MUST have 5 syllables, the second line MUST have seven syllables, and the third line MUST have 5 syllables. I even managed to get a (sort of) inspirational message in. But it doesn't sound like poetry. Why? Maybe because I could say that just as well normally: "The smallest minnow is food for the largest shark. It's still important." Anyhow, it's not great. Can you do better? Try it.