Zeolith is a solid natural stone which contains many pores, cavities and channels. Hobby Zeolith works in an adsorptive manner, i.e. environmental toxins and decayed products are directly attracted and retained by the system of cavities through strong electrostatic fields (e.g. up to 90% of ammonia). Zeolith has a huge internal surface area. Approx. 10 gram corresponds to the size of 4 football pitches. The cavities are 4 millionths of a millimetre in size, a dimension into which an ammonia molecule fits exactly.There is a sustained reduction in the phosphate content due to the fact that the formation of natural bacteria and microbes is actively encouraged. Zeolith acts as an ion-exchanger and catalytic converter. The water becomes softer, clear and free from toxins. Zeolith also promotes fast growth of bacterial cultures which convert nitrogen and fix and break down organic by-products. 1 kg Hobby Zeolith is sufficient for 500 l of water and remains effective for approx. 3 months, assuming average fish population levels.The grain size of Hobby Zeolith 500 g and 1000 g is 5-8 mm, the 10,000 g package has a grain size of 8-16 mm.