If you have been following this thread, you will realise I have been following the manual closely
The manual has suggestions of media and one of them is the pellet things which they call "peat granules", but could also be carbon - which is also in the manual. However I will try to get what? "Sintered glass media"? Sounds owie when cleaning! :-?
Failing that, if the shop doesn't have it, any other suggestions please?