Difference Between Pneumatic Pressure Gauge and Hydraulic Pressure Gauge?

Can we use same pressure gauge for pneumatic and hydraulic applications?

Case:

We are using the test rig for checking the leak in the assembly. The leak will be checked by means of pneumatic and hydraulic by using compressed air (10 bar) and RO water (20 bar) respectively.

The result should be "No leak" in the assembly and "No pressure drop" in the pressure gauge. Can I use the same pressure gauge for both the applications? Is there any difference between pneumatic and hydraulic pressure gauge?

Please advice.