Set up routines and transfers between debit cards, just as you would with ACH Accounts. When transferring between debit cards, the payment_type parameter in the transfer object must be set to debit or else the request will fail. For example, if the payment_type between two debits is set to ach, the transfer will fail. Inversely, if the payment_type between two ACH accounts is set to debit, the transfer will also fail.
Please see the section on The Transfer Object to learn more.
Note that Transfers between an ACH account and a debit card are not available.