  About 70\% of the Universe is Dark Energy, but the physics community still
does not know what it is. Delta Gravity (DG) is an alternative theory of
gravitation that could solve this cosmological problem. Previously, we studied
the Universe's accelerated expansion, where DG was able to explain the SNe-Ia
data successfully. In this work, we explore the cosmological fluctuations that
give rise to the CMB through a hydrodynamic approximation. We calculate the
gauge transformations for the metric and the perfect fluid to present the
equations of the evolution of cosmological fluctuations, providing the
necessary equations to solve in a semi-analytical way the scalar TT Power
Spectrum. These equations will be useful for comparing the DG theory with
astronomical observations and thus being able to constraint the DG cosmology,
testing, in the future, the compatibility with the CMB Planck data, which are
currently in controversy with SNe-Ia.
