Having trouble with control array

sorry if this is a noob problem.

I have 30 pictures in a control array and i keep getting an error message that says control array element 31 does not exist

Private Sub tmrbarrel_Timer()
For i = 0 To Image3.UBound
If Image3(i).Visible = True Then
Image3(i).Left = Image3(i).Left + 25
End If
Next
End Sub

Private Sub tmrcounter_Timer()
i = i + 1
Image3(i).Visible = True
End Sub