We found an interesting article from a Japanese blog regarding what's inside the Brita Maxtra filters. According to the blog article the water filters use Coconut shell active carbon and Small ceramic beads made of mineral stones, such as zeolites.
Similar type of "zeolite balls" used inside the Brita filters, we tried using our "Zeostone" Size 2 for filtering fish tanks and aquarium waters. Also tried for our drinking water for ourselves. Seems to work out fine. Our ball type zeolites are heated in extremely high temperatures to minimize the dusty powders of the zeolites.
Zeostone Size#2. ( 2mm zeolite balls ) http://amzn.to/1KvQKY0