Hydro when connected to the P4 is controlled via the 1-10v port. You get the same options within the stream group options. The hydro app offers more options thou.
You would use the hydro app for the control of the pumps and the 1-10 for maintenance and feed mode options from the P4.
You would use the hydro app for the control of the pumps and the 1-10 for maintenance and feed mode options from the P4.