Matrix Gel with arnica is a medicinal and high viscosity gel that is ideal for conductivity. Plain Aloe (with no additives) works, however it breaks down quickly and the patch will need to be check in the morning and evening to insure the light is still on. Matrix also offers a plain, no additive, high viscosity ultrasound gel.
A few tips and information on using microcurrent to treat horses. Electrodes include pad electrodes, black carbon electrodes, silver knit, and more.