In general, all gels should work with the cap (see this EasyCap document on electrolyte gels). However, if you had already used the gel that contains saline before, the water-based gel performance may be significantly worse, as the electrodes may still contain salt remaining. If this happens, please clean the electrodes entirely before using the water-based gel. You can always try and see if your gel provides you with the satisfying impedance values, before starting the experiment. If not, we suggest you contact EasyCap directly, to get further help with this issue.