Cardano fees are based on transaction size. Fees do not vary based on network activity or prioritization and are therefore not editable. Learn more about the Cardano fee structure.
The Cardano protocol states a minimum ADA value for transfers, in order to avoid dusting the network. It is important to state that this minimal value is defined by the network, depending on the network 's current state. The exact calculation can be found here. On Fireblocks, we do not allow estimation of an “unrealistic” transaction. Therefore, when you query the estimate fee endpoint with an amount that is considered below getMinUTxOValue (dust), the endpoint will drop and fail the request, in the same way that the blockchain will reject the transaction if it is submitted with this amount.