Replacement di de ionising resin for the de ionising pod suitable for all di needs this 1 litre bag will refill your d d di pod over 3 times r r why should i use a de ionising resin after my ro unit normally it is not necessary to use a de ionising resin after an ro unit as for most aquarists the water quality is well within the levels required which is why as standard we supply a 3 stage systemsome people however want to remove all traces of salt from the water and by utilizing a de ion