[TheOldSalt]

I haven't tried this with serpulid worms, only sabellid worms, so I don't know how important species is. The typical brown & tan banded ones you see most commonly work well enough.
If they're attached to liverock, then poking them from behind would probably prove a bit tricky, eh? If you can do it, though, then it shouldn't matter.
Using waterchange water might be okay, but just keeping the system free of mechanical filtration & skimming until the larval worms have settled and then feeding with DT's or refugium algae scrapings should work fine. I used to do this fairly regularly in natural freshly collected seawater full of plankton, but the DT's should make a good enough substitute.
Come to think of it, dumping the eggs into the refugium and restricting the flow for several days while the larvae settle would probably work best of all.
They should of course be adult size in order to ensure full gamete production.