this may sound stupid...but do beneficial nematodes have any bad effects...like killing earth worms or any thing negative for that matter?

There are literally trillions of soil microbes, and dozens of different species of soil micro-organisms in compost and in healthy soils. Bacteria, fungi, actinmonycetes, protozoa, nematodes, etc.

There are good and bad nematodes in soils. The good nematodes actually kill or repel the bad ones. The good ones naturally live in good homemade composts, just like aerobic bacteria and fungi. Some folks (not me of course), purchase lots of extra beneficial nematodes from commercial farm centers to add to their soils, to do their magic disease/pest control abilities, because their soils are not rich enough or healthy enough to have enough "good" microbes in it from constant and abundant composting and/or cover cropping.

Earthworms, sowbugs, centipedes, etc. are larger soil organisms. They are all in no way harmed by any of these "bad" microbes, as long the compost is rich, and aerobic, and thriving with the strong, disease and pest fighting aerobic microbes inside of it.

thanks capt.