u/Ashduff

I am 100% sure I saw a big snail leech pop in and out of one of my large snails in an establishing tank yesterday. i put the snail in a closed breeder box within the tank for now but looking for what to do? it's a 20g long that i'm maturing with only snails in it, one mystery 2 rabbit one spixi (leech) and assorted ramshorn,bladder, and one pond. the infected snail was gifted to me recently with the other large ones

main 2 questions:
what thing do i put in the water to kill the leech? ideally without killing snails but if so ill remove my large ones and as many small as i can then do it

what do i do with the actual infected snail beyond isolate?