Beneficial soil nematodes

where do I get more? Or breed them? or something...are they even important?
The guy at the grow store looked at me like I sprouted a third arm or something...he basically sticks to hydroponics and is of little use to me.

I'm looking at a pile of sterilized soil after a white fly invasion and wonder what havoc have I wrought?

i see you around a lot...would love to see a grow pic or two....