We have always used the disposable type available from the supermarket or diy shops, or the ones which have a sack of crystals on a tray over a catcher. Just stand it in the sink in case it over flows or falls over. We find they are easy and effective.
We have decided to try this option too, although Mr Trumble Too wanted immediate evidence that it was working !! 😯 😕 😯 😆
Thanks for all your helpful advice