You normally don't need 50 volts.
The reason you need more volts than 10 going into your power module is so that the module has voltage available to control the current. So if the cell resistance becomes high (like raising the cathode), the module can apply more voltage to maintain the desired current, and if the cell resistance is lower, the module can decrease the applied voltage to bring the current back to the desired level. Current equals voltage divided by resistance.
BUT remember the 10 volts minimum is for an electrode spacing of 1.5 inches (37mm)
At 2 inches, you need 12 volts
At 3 inches, you need 16.5 volts
This is to provide the same electric field strength which propels ions from one electrode to the other.
Required volts = 4.33 X Spacing in inches plus 3.5
Higher ppm does not require higher volts.