I've had great success with this species. Converting them to frozen food is possible but not easy. And relying on natural fauna within the aquarium is rarely successful. Here's what I did:
I quarantined 4 of them in a cycled bare 15 gallon with just some PVC pipe for hiding places. To initiate feeding I started them on newly hatched LIVE baby brine shrimp. They ate this very greedily, as I assumed it had been a while since they ate. Hatching artemia on a daily basis is MANDATORY if you're going to be successful with them. After a couple weeks on enriched artemia, I started introducing cyclopeeze and frozen mysis before I added the artemia. Only once they were eating this heartily did I start weaning them off the artemia.
Adult brine shrimp don't work and have very little nutrition. You can try live tigger pods but are astronomically expensive because of the massive quantity these pipefish will eat. I have never seen them refuse newly hatched brine shrimp, it's just a pain to hatch them every day.
I have used this method with janns, banded, yellow banded, bluestripe, and dragonface pipefish. They all converted to frozen for me but I would never have been successful without the artemia. So BEFORE you try again with another group of pipes, get started on your hatching brine shrimp skills!!! I recommend just start hatching them now. And any extra can go into your reef tank, corals love the stuff!
As a side note, I ended up separating them into 2 tanks. Pairs are VERY intolerant of others in the same tank. I lost one to a bacterial infection from a wound the pair had caused him. So If you have more than one, make sure you have available space to separate them.