Spaghetti worms are available many places. Two commercial sources online that I know of are IPSF.com and InlandAquatics.com. Both great businesses, and would be able to get you lots of spaghetti worms. Many people on this and other boards also sell detritovore packages from their tanks, and include Spaghetti Worms.
I myself have a lot of them all over my tanks, and find they are awesome at cleaning up. Even when feeding heavily, after a few minutes, all the stuff that was drifting through the water and collecting on th sandbed, has started to form clumps. A few minutes later, the clumps have all these tentacles appearing around and outside them. A few minutes later... and the clumps of extra food are gone.
Great Animal to have in a tank. They do well in Sandbed's and on LR as well. So long as the Rock is Porous and there's somewhere for the worm to place it's bodie, you're A-OK.
- Mac