I recently returned from a trip to China where we had wonderful hotpot - both Mongolian-style and Sichuan. In Bejing, we found a Sichuan place that started our broth as water and a Mongolian/Northern-style place that had several mushroom-based broths. With these methods, we were able to have non-meat (but with fishball) hotpots. In the Sichuan place, the pot was divided in half, so the meat eaters could indulge without 'contaminating' the fishy side.
Do any of the hotpot places in the LA area offer similar options?
BTW - review of my favorite of our Beijing hot pot experiences on the China board: