What is the minimum pH at which Cr(OH)3(s) will precipitate from this solution?

In a particular solution, [Cr3+]=2.3x10^-5 mol/L. What is the minimum pH at which Cr(OH)3(s) will precipitate from this solution? ume the temperature is 25oC. For Cr(OH)3(s), Ksp=6.3x10^-31 at 25oC.