Mine never do.... Assassin snails are a prevention mechanism not a cure for snails imo, they keep the numbers down but my "pest" snail community keep on in good numbers, mine seem to have a preference for pond snails though and judging by visibile numbers leave the ramshorns relatively untouched. I have assassins, Malaysian trumpets, dominican trumpets, ramshorns and pond snails all in the same tank and the 3 assassins stop numbers from getting excessive and fortunately I saw them breed although it does take 6 months for the babies to be recognisable