Flourite substrate is specially fracted stable porous clay gravel which helps nourish plants and their roots, and as it is natural it never needs to be replace like other laterites. It works best on its own but can be mixed with other gravel.Flourite comes in 4 different colours and more or less colour is down to aquarist colour desire. There is a slight difference between the colours of nutrients/elements released for the advance aquarist looking for something particular please refer to seachem chart at www.seachem.com