when i had them i crushed the ones on the sides and the eggs then out a potato in and the snails are attracted to the potato so every day remove the potato with snails on, takes a while but eventually gets rid of them
$10 a heat pad is quite a lot if you get them off tm or off people off here they usually are $3-4, also try New World as i got a poly box for a New World in Taupo for $1