... hum.. needs like u need some trining to do on him.... i had the same problem at first.. heck.. i had a really big problem.. ( 7'' lunnar and 6.5'' tusk )
u just gotta kinda feed them right.. and kinda teach them like what to eat... not only that but try shortening your light 'on' time some... as much as possible i say... cuzz feeding the fish will make him less likly to eat other thigs when he's full....
but one of the main thing your doing is teching the snails to be somewhat nocternal like.. so they will learn to burry themself in the day and come out at night to eat.....
this may sound kinda weird but i did this.. and now i i hardly lose n e snails..( i only have about 25 or so) .... not only that but im in the process of turning my agressive into a agressive / reef.... i currently have a hammer and sone shrooms in the tank.. no probs at all so far...