•Three small solar ponds with three different salts have been studied.•Crank Nicholson scheme has been used to solve the bi-dimensional heat diffusion equation.•Good agreement between numerical and experimental results have been obtained.•The salts used were NaCl, Na2CO3 and CaCl2.•CaCl2 responded more quickly than the two formers. We consider three experimental small solar ponds (1m×1m×1m) each pond contains one of the following salts, namely NaCl, Na2CO3 and CaCl2 respectively. The thermal behavior of these three ponds is being investigated numerically and experimentally over a period of 28days. A bi-dimensional heat diffusion equation has been resolved numerically using the finite differences scheme of Crank–Nicholson. The experimental results show a good agreement with those obtained by simulation with an error of less than 1.5%. This study shows that CaCl2 pond responds thermally more quickly than the two other ponds without reaching saturation. This extends further the applications scope with possible higher temperature despite relatively its higher cost which deserves further investigation.