Replacement filler is cheap and it's probably just a matter of time before you try the vaunted aquirum filter blue foam.
I bet that's true!
There is a fantastic youtube video where a guy goes
through step by step of how to clean your 510 cartridges, but I can't find the link for the life of me. Basic jist is this:
1. Remove filler from the cartridge. You may wash this out with hot running water and squeeze dry if you want to reuse it, or you can purchase new polyfil at WalMart or a craft store to replace it, or you can purchase Marineland U shaped blue foam from PetSmart or another pet store and use that to refill with.
2. The mouth piece (aka cartridge) comes apart into 3 parts. Using a paper clip, pop off the end piece you put in your mouth. Right under that is another disc shaped piece of plastic. Remove that as well. You should be able to see most of the way
through the cartridge now.
3. Place all pieces in alcohol to soak and sterilize for about 15 minutes. Some people use isopropal, but I use either 100 proof liquor. Everclear or vodka will get the job done.
4. Dry off your pieces and reassemble.
5. Re stuff your cartridge with the filling of your choice.
Sounds like a lot of work, but I do about 20 carts at a time and it takes about 5 actual minutes of work. It's a good idea to clean your equipment. After all, you are sticking this stuff in your mouth.
Good luck!