I just purchased a pack of pot sponges and pot scurbbing pads to use as a replacement for the cartridge filters. However, the problem I have encountered is that there is no real slot for these to slide into. The cartridges that I am attempting to use are from a whisper HOB and pengiuin HOB. What have you all done to modify these cartridges to allow the sponges/pads to work? Use some sort of adhesive (sylicone), buy a different cartridge of similar dimensions that allows you to insert the pads, etc?