i do have these leeches on my tylos(and since removed), but not as abundant as your stocks. my method is salt bath for 10-15 mins. normally the leech will just move away from the host but sometimes i have to manually remove them from the snails.
i have brought these guys in probably a dozen times now and have never had this happen before. I feel like I have leeches crawling all over me, its terrible, lol
you know, its really hard to tell as they were soooo infested and weak when i went that course. I don't think so. I think that if the prazi was going to take them out, it would have taken all of them out. I certainly wouldn't recommend a prolonged bath for them, but it sure paralyzed/knocked out the bulk of the leeches.