A liquid in a given capillary tube always rises up to a fixed height but not infinitely why

The answer is; the density of the liquid suppresses the height to which it can rise

The density acts in the opposite direction of capillary action. Capillary action allows the liquid to rise in the tube and the narrower the tube the higher the capillary action and the higher the liquid rises. The denser the liquid however, the lower it will rise. The column stops rising when the capillary force is balanced by the weight of the rising liquid due to gravity.