Posted: 11/05/2014 at 18:46
Nematodes are microscopic worms which you water on the soil and are completely safe. In fact, there are nematodes in your soil anyway, but 'Nemaslug' (the one to google for) just adds lots more which will kill any slugs in the area where you water it in. It doesn't kill snails though, so best go out with a torch at night to see whether it is slugs or snails (or both if you are unlucky!)
Do be aware that other things may be to blame though, including squirrels, birds (esp. pigeons) and rodents.