Given the large amount of future data on large scale galaxy clustering expected from DESI and EUCLID it is of foremost importance to understand what information about the nature of the dark sector can be extracted from these measurements. In this context, I will investigate the imprints of new long range forces acting solely on dark matter. First I will show how the EFT of LSS can be extended to include these new forces making it possible to get reliable predictions in the mildly non-linear regime of matter fluctuations. This allow to forecast the future sensitivity of an EUCLID size survey that will probe dark fifth forces down to coupling strength one per mill weaker than the gravitational one. At non-linear level the presence of fifth forces induces violation of the equivalence principle in cosmological correlators. I will show under which condition these could be directly tested in the bispectrum of two different tracers with near future galaxy surveys such as DESI and EUCLID. Finally, I will comment on the expected behaviour of the LSS correlators varying the range of the dark force.