Just cut off a piece of your sponge and use. It doesn't have to be a large part but attach it to the new filter and it will speed things along by a lot! I always keep an extra sponge filter bubbling along in the back of one or another of my tanks so I have one in an emergency but I also keep Bio-spira all the time too. But the extra filter works best in a q tank when you do not want to have the sick fish exposed to any
ammonia as Bio-spira does have an ammonia and
nitrite spike associated with it even though they are small.
Rose