The USB pumps can be used with only a 4 pin aquabus connected to the AQ5 but it limits the Aquasuite interface.
The Aquaero can control the speed of the pump just fine either way, its just that the monitoring functions are limited to USB connection.
for example;
This is an overview with one pump connected via USB + Aquabus and one connected via Aquabus only. You can see that D5 USB 1 is shown as USB cable not connected.
In the outputs tab both pumps look the same
and both pumps can be added to controllers just the same.
But to have the pump speed and pump power available on the Aquasuite overview it needs to be connected via USB
In my overview only pump speed etc is available for pump 2, the pump connected via USB
When you add a chart or guage to Aquasuite you are given a list of available sources
You can see how pump 1 does not have any available sources, only the AQ5 and pump 2 have available data sources.
When only the AQ5 is connected via USB then only the AQ5 data sources are available for display in Aquasuite.