Tiny "Worm-like" (not earthworms or grubs) critters in my soil

While amending and planting the beds in our new house, I have noticed some areas are infested with tiny (@ 1/4" - 1/2" long) dark, skinny shiny little worms that curl into a "c" , then "play dead" when disturbed. They have no discernable legs, not millipedes or centipedes, and they are not pill bugs. They are just under the surface of the soil. Are these what are called eelworms?

The existing soil was totally depleted, hard, acid clay if that paints a better picture.

What are they exactly, and what do they eat? Are they beneficial or harmful? (I'm guessing the latter). If that's the case, how do I get rid of them, preferably without chemical controls?

Thanks!

 

could be wireworm