In this study, the utility of zeolitic tuffs obtained from the Bigadic (Balikesir) region was investigated as an ammonium ion exchanger and decolorizing agent. For this purpose the adsorptions of ammonium ions and methylene blue from aqueous solutions on the zeolitic tuffs were studied the batch equilibration technique as a function of adsorbate concentration. Adsorption isotherms were described using the Langmuir isotherm model. The effects of thermal treatments and acid activations on the adsorption capacity of tuffs were also examined.