i would say NO because you never know what chemicals the worms have come across which then could be passed on to your fish and then they could die, and you dont want that do you?
i heard you could but i would be careful maybe you should get a smaller tank and fill it with soil keep digging in leaves as food and keep the earth worms in there for a while this will help ensure that they havent come into contact with the chemicals
also if you soak an old towel in water and layit across you lawn they come to the top within a couple of hours
When I was breeding geophogus, I would have gone broke if it wasn't for using live earthworms. I only use the ones from my own organic compost heap, and rinse them well first. Bettas love the tiny ones, lol.