No, this is not about the composition of the mattress or the question of who sleeps at the window: A MIXBED is the mixture, or the combination of strong acidic cation and strongly alkaline anion exchangers, which are fixed within their container (fixed bed). During regeneration, i.e. cleaning for subsequent reuse, the two components are processed separately and then brought back together again. Mixbeds are used to produce demineralized water.