No problem. I'm guessing, by your reply, that there isn't enough space in the other disk group to hold both? If there were then it's pretty easy. However, since you are saying it is split then I'm guessing you are using most of the space in both?
Anyhow, another option is to just purchase more disks and add a third disk group to the pool. Then it will be non-disruptive when you delete the affected disk group. Expensive option but less impact. Please update the thread if you discover another option from support.
Just reinforcing that each disk group in, in a pool, should be identically configured in each disk type/tier. So, if your first disk group is 10 x 1.2TB then the rest of the "standard" tier disk groups should be configured the same way so as to avoid potential performance issues and hot spots. If you add a new tier (i.e. nearline for 'archive' or ssd for 'performance' then those disk groups can be configured differently if needed).
Thanks
Mike