Good question. They are part of the food soil web and this is just from a soil sample from the garden. Depends on the species as to what they are up to. I am going for regenerative soil practices on a small scale so its easier to do and have never had any of the problems associated with problem nematodes like root feeding nematodes .

The only nematode I have ever intentionally added to the soil here was years ago and was the one for slugs Phasmarhabditis hermaphrodita, it could be that one. I definitely have fewer slugs than I did when I first came here, to me it looks similar but really I am very new to identifying nematodes so at this point couldn't say for sure. Would be interested what your expert friend thinks.