I have a Aqua-Tech 30-60 HOB filter. The bio-filter which said you never replace has become worn and falling apart from getting rinsed out so much and I can not find that kind of material to replace it. So does anyone have any ideas what it is or would you just replace it with something else? I thought about just putting some bio-glass in a media bag and slideing it down in front of the filter cartridge.Do you think that would work?