The dynamics of large fractal colloid aggregates, which were described by a combination of translational and rotational diffusion and internal elastic fluctuations, were investigated. Light scattering was used to measure dynamics of colloidal aggregates formed both in microgravity and on Earth. The comparison of results obtained in microgravity and on Earth demonstrated that cluster growth is limited by gravity-induced restructuring. The results show that in the absence of gravity, thermal fluctuations ultimately inhibit fractal growth and set the fundamental limitation to the lowest volume fraction which will gel.