The best replacement for nematodes is roundworms.

The best alternatives to nematodes are rated as following:
★★★★★  roundworms
★★★★★  annelids
★★★★★  earthworms
★★★★  milky spore
★★★  planaria
★★  platyhelminthes
★  cestodes
★  insecticide
★  trematodes
  diatomaceous earth

Your alternative for nematodes is not listed? Suggest!
Speaking about nematodes, one probably shouldn't forget about tarantula.

Other search terms related to nematodes and their ratings are:
★★★★★ tarantula
★★★★ grubs
You have in mind a companion for nematodes and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of nematodes in all years. Click on graph for more.
nematodes
roundworms
annelids