If this is the wrong forum I am sorry...

My green tree frog and pacman frog both got new soil a few weeks ago. I looked closely at the soil (mostly the wetter parts) and there are hundreds of little black worms. A 1/4 of an inch long.

I threw everything away because I hate worms and I freaked out a bit. What are these? Are they parasites? What can I do to prevent these in the long run?

Thank you for any replies