Kind of a waste of a 120 to put pipefish in unless you plan on going all the way with it. Pipefish have very similar requirements to seahorses. They pretty much only eat live food, they are out competed by finned fish for the food. Now they can be trained to eat frozen food, although some species are easier to train than others, local ones from here for example seem to eat frozen mysis like they have been doing it all along, while some banded I had would touch the stuff. You are also very limited in fish and I recommend you stick with other sygnathids like other pipes or peaceful slow moving fish.
Best thing I can think of starting at square one if you want pipefish is to order your rock at a 50% live 50% base ratio. Make it uncured and straight out of the water from one of those places in FL who aquaculture it and let it sit in the running tank for a few months doing standard SW care for the tank. After the first month get a couple chromis and put them in there and let them be the guini pigs to make sure there arent any bad critters from the rock. catch the bad critters that inevitably show up. Meanwhile your pod population should be growing greatly. After several months start adding pipes. You could easily go with multiple dragonfaces although I wouldnt. I would go with 2 or 3 pairs and go on to the next species. Do your research on the species, certain ones will go with certain ones and if possible, stick to species from the same ocean for disease reasons. Add them slow train each new one to eat frozen before added the next set. this plan has worked for me in the past although I had a much smaller tank to work with.