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/www.drsfostersmith.com/product/prod...=2004&Nty=1
There are 2 sponges stacked on each side. I just get the replacement filters and sew up or cut the hole to fit on the intake. Then sew up the hole on the bottom. Any soft filter sponge would work. They don't reduce your flow because they are made for filtering water. They also boost your good bacteria and pre filter so the bad stuff doesn't get to your impeller. It saves on floss too. Another plus is fry don't get sucked up. All you do is rince really well in old tank water and put it right back on. If you check around you will find that sponge filters come in all sizes and shapes. All you need is the replacement sponges. They are usually very cheap.
As for the floss... it is the same thing as the poly stuffing at craft shops for pillows and stuffed animals. You can even use cotton balls. I have done that when I ran out before my shipment came. I have used new cloth diapers and washrags too.
Coffee filters are good for polishing in a pinch.... So many things...