I feel somewhat out of place amongst all you Kiwi's :-)
Anyway, my Oscar tank is infested with Malaysian trumpet snails. They are absolutely horrible, they get everywhere, in your filters, all over the glass, in the gravel, you name it, you will find them. I even went out and bought two huge clown Loaches which cost me a small fortune. I have seen them with snails in their mouth a couple of times, but they haven't really made a difference to the population. These snails are absolutely unbelievable, they breed like rabbits. Unfortunately I haven't been able to find a solution to get rid of them. If anyone has got any ideas, please do enlighten me.