Unflavored metamucil is psyllium husk... as to why you might add it is that some consider it a good replication of dry grass seeds that might be in a field mouse's innards for example. Sometimes fiber can be useful with diarrhea and with individual cats.
Florastor as a probiotic seems to be getting a lot of anecdotal approval by pet owners, I've not used it yet. I also recommend Proviable especially in cases of bad diarrhea as it comes in a paste form that has kaolin and pectin that can soothe the digestive tract and help manage the diarrhea while the probiotics help repopulate the gut to become healthier. Recently this has aided a rescue cat we have in foster care who arrived with watery stools while we are waiting for the compounded tritrich meds to arrive..
Florastor as a probiotic seems to be getting a lot of anecdotal approval by pet owners, I've not used it yet. I also recommend Proviable especially in cases of bad diarrhea as it comes in a paste form that has kaolin and pectin that can soothe the digestive tract and help manage the diarrhea while the probiotics help repopulate the gut to become healthier. Recently this has aided a rescue cat we have in foster care who arrived with watery stools while we are waiting for the compounded tritrich meds to arrive..