Hello,
When you create a custom token using the Fiat Coin adapter, this balance works the same as the balance of any other type of coin: It is the sum of transactions affecting that user.
The wallets_api_balance filter returns the current user’s balance. You do not need to periodically query this API, it is only for letting you know the total user’s balance.
Could you please explain in more detail what you are trying to do?
thank you