Hi Bel.Is it a nature pond or does it have fish in it? The former will be fine,as they will be kept in check by other water creatures,some of which,if carniverous, will eat the snails.However if you have them in a fish pond they can be hosts to parasites that can affect the health of fish and they are not a good idea if in large numbers.
If that is the case i recommend you remove as many as you can,though you will never get rid of them,and put them into a nature pond in the wild,or give them to someone who has a natural pond, as in reasonable numbers they are beneficial .