I also bought mine from Inland Aquatics. It's not cheap when you factor in shipping so you want to order enough different things to make is worthwhile. They good news is that once you have a viable population they reproduce like crazy in our systems.
The other possibility is to swap sand with an lfs or fellow reefer that has them. Might try a local reef club if you have one.
I think spaghetti worms are the most beneficial sand infauna you can have. They eat any organic detritus that hits the sand in my experience.
If you want, you can Email me your address and I will try to mail you some USPS priority mail in a small container-not sure they will make it, but should. It may take me a week or two, however, to get to the PO (have an infant and in the process of buying a house). I have several spaghetti worms every square inch of bed, on the rock, and in the skimmer, etc. They are always on the move around the tank to find more room.
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