No you don’t, but it’s not a bad idea. There are three main reasons for using a decanter. Firstly, bottles kept for any length of time in a dusty cellar can look dirty and unseemly on a table, with the contents more elegantly displayed in a pretty glass receptacle; secondly, old wines need to be separated from their sediment so that the gunk doesn’t end up in your glass and, thirdly, a red wine’s flavour is generally improved by being allowed to ‘breathe’. Don’t panic if you haven’t got a fancy decanter, use a jug. Or pour the wine into an empty bottle, sluice out the original bottle and pour back.