I think you could keep blue striped pipefish. They're small enough for a 30, tolerate reef conditions, and are feisty themselves. They do have some specialized needs, but they're probably the best reef pipefish.
First, if you want more than one you want a male/female pair. Otherwise they'll fight. The males are distinguishable by the spikes on their nose, though you might need a magnifying glass to see that.
They might require live food to start, I'd plan on getting live brine shrimp (adults) and hatching brine shrimp to start. Most switch to frozen pretty quickly though. Mysis and nutramar ova seems to be preferred. I've had mixed results with cyclopeeze.
You will have to protect any intakes and overflows so they don't get sucked up into them. They can fit in very small crevices. They also can't be kept with stinging corals (most LPS), anemones, or claims.