I stopped using the fishtank-filter a while back, because it had the same drawback as the filler of the e-Cig cartridges (both empty or filled ones): the filler itself soon gets pushed together, and then doesn't reach the atomizer-bridge anymore (so you have to keep messing around with it, pulling it up, putting straws underneath to keep it up, whatever). From then on I just bought some Janty- and Partysmoker cartridges; emptied them, then rinsed and kept re-using them. Would be okay for a while, but of course this didn't work endlessly, I had to buy new cartridges with some regularity (filled ones, neither sell empty cores) to keep my stock filled. Well... a few weeks back, one of my young dogs tore it's fluffy toy in pieces within an hour after she had gotten it (my avatar was the guilty one ). And as I was cleaning up the mess, it suddenly dawned on me that the filling of that toy was real spongy-feeling: I could press it together and it would come right back up to it's original space-filling all the time... It looks the same as the fishtank-filter, also very clean and with no loose small pieces of thread in at all; but it feels and acts much better as to what we need for cartridge-filler. Washed some of it and tried it; and indeed, this is a real step forward, works much better! Then I made small holes in other fluffy-toys I have laying around.... and they all had the same stuff in them (from different brands and different sellers). So it looks like all or many fluffy toys have what we need inside them Not sure if it's just pet-toys or also children-fluffy's that have the right stuff: only have pet-fluffs around the house here. I can't track it down on internet in unused state... can't afford to keep buying and discarding like probably would be neccessary until stumbling upon the exact same stuff. But perhaps someone here by chance would happen to know where these kinds of toyfillings come from? And anyhow, for now I will manage with the toys, though it's no cheap way of getting filler... but one toy's innards should last a year or so I think. So from now on I am getting a new pet-toy myself once a year!