That's because its a silly click baity question designed to generate participation and clicks. A water change is not a filter.I think the question is awkwardly worded. If you actually look up the definition of the word 'filter'. It is passing liquid/etc through a device to remove something. In that sense - adding bacteria is not a filter. IMHO - the question is asking 'Can water changes act as a filter by removing undesirable chemicals from the water'. The answer to that question again only my opinion is yes.