Hi there. I have had my two goldfish for 5 years and have never changed the filter sponges (I just squeeze them out whilst doing my weekly water change. They have lost their shape and become thin and floppy. I don't want to completely replace them as they contain the bacteria necessary to keep my tank healthy for the fish. Can I put some new sponge in with the old one behind the other sort of thing or do I cut some off the old sponge and put new sponge besides it? As there are two of these sponges in my fluval filter should I remove one and replace it with new sponge? Ive been googling but can't find an answer. Can you please advise?