In order to calculate the acceleration due to the geopotential, I've already implemented the EGM-2008 TideFree model, getting the coefficients from the link.
Is the Earth tides effect already considered in these EGM-2008 coefficients? If not, how to measure the effect of tides?
To implement the effect of harmonics, I calculated the gradient of the geopotential $\nabla$U (equation was taken from Vallado). Using the symbolic math library in Julia language, the program is able to calculate the harmonics effect for any given degree and order.