Gradually mixing in your tank water over a span of 1 to 2 hours should do the trick. Not very different from how you acclimatise your fish.
Btw, what and how many fish do you keep? Are they reef (i.e "feather duster/tube worm") safe? Generally speaking, triggers, pufferfish, filefish, boxfish and butterfly fish are a "no-no".
As southpaw said, your water conditions need to be optimal for the coco worms to thrive, unlike some of the other more common tube worms.