Why isn't hexaaquairon ion a hydrate?

What is the difference between hexaaqua(metal) ions $$\ce{Fe^{3+},Al^{3+}, Cr^{3+}}$$ and a hydrate? Since both of these absorb water into it own molecular structure. Would it be that hydrates have neutral charges where as these have positive charges? Why did we name Hexaaquairon ion it's name rather than Iron(3) Hexahydrate.


